/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Ben Widawsky <ben@bwidawsk.net>
 *    Michel Thierry <michel.thierry@intel.com>
 *    Thomas Daniel <thomas.daniel@intel.com>
 *    Oscar Mateo <oscar.mateo@intel.com>
 *
 */

/**
 * DOC: Logical Rings, Logical Ring Contexts and Execlists
 *
 * Motivation:
 * GEN8 brings an expansion of the HW contexts: "Logical Ring Contexts".
 * These expanded contexts enable a number of new abilities, especially
 * "Execlists" (also implemented in this file).
 *
 * One of the main differences with the legacy HW contexts is that logical
 * ring contexts incorporate many more things to the context's state, like
 * PDPs or ringbuffer control registers:
 *
 * The reason why PDPs are included in the context is straightforward: as
 * PPGTTs (per-process GTTs) are actually per-context, having the PDPs
 * contained there mean you don't need to do a ppgtt->switch_mm yourself,
 * instead, the GPU will do it for you on the context switch.
 *
 * But, what about the ringbuffer control registers (head, tail, etc..)?
 * shouldn't we just need a set of those per engine command streamer? This is
 * where the name "Logical Rings" starts to make sense: by virtualizing the
 * rings, the engine cs shifts to a new "ring buffer" with every context
 * switch. When you want to submit a workload to the GPU you: A) choose your
 * context, B) find its appropriate virtualized ring, C) write commands to it
 * and then, finally, D) tell the GPU to switch to that context.
 *
 * Instead of the legacy MI_SET_CONTEXT, the way you tell the GPU to switch
 * to a contexts is via a context execution list, ergo "Execlists".
 *
 * LRC implementation:
 * Regarding the creation of contexts, we have:
 *
 * - One global default context.
 * - One local default context for each opened fd.
 * - One local extra context for each context create ioctl call.
 *
 * Now that ringbuffers belong per-context (and not per-engine, like before)
 * and that contexts are uniquely tied to a given engine (and not reusable,
 * like before) we need:
 *
 * - One ringbuffer per-engine inside each context.
 * - One backing object per-engine inside each context.
 *
 * The global default context starts its life with these new objects fully
 * allocated and populated. The local default context for each opened fd is
 * more complex, because we don't know at creation time which engine is going
 * to use them. To handle this, we have implemented a deferred creation of LR
 * contexts:
 *
 * The local context starts its life as a hollow or blank holder, that only
 * gets populated for a given engine once we receive an execbuffer. If later
 * on we receive another execbuffer ioctl for the same context but a different
 * engine, we allocate/populate a new ringbuffer and context backing object and
 * so on.
 *
 * Finally, regarding local contexts created using the ioctl call: as they are
 * only allowed with the render ring, we can allocate & populate them right
 * away (no need to defer anything, at least for now).
 *
 * Execlists implementation:
 * Execlists are the new method by which, on gen8+ hardware, workloads are
 * submitted for execution (as opposed to the legacy, ringbuffer-based, method).
 * This method works as follows:
 *
 * When a request is committed, its commands (the BB start and any leading or
 * trailing commands, like the seqno breadcrumbs) are placed in the ringbuffer
 * for the appropriate context. The tail pointer in the hardware context is not
 * updated at this time, but instead, kept by the driver in the ringbuffer
 * structure. A structure representing this request is added to a request queue
 * for the appropriate engine: this structure contains a copy of the context's
 * tail after the request was written to the ring buffer and a pointer to the
 * context itself.
 *
 * If the engine's request queue was empty before the request was added, the
 * queue is processed immediately. Otherwise the queue will be processed during
 * a context switch interrupt. In any case, elements on the queue will get sent
 * (in pairs) to the GPU's ExecLists Submit Port (ELSP, for short) with a
 * globally unique 20-bits submission ID.
 *
 * When execution of a request completes, the GPU updates the context status
 * buffer with a context complete event and generates a context switch interrupt.
 * During the interrupt handling, the driver examines the events in the buffer:
 * for each context complete event, if the announced ID matches that on the head
 * of the request queue, then that request is retired and removed from the queue.
 *
 * After processing, if any requests were retired and the queue is not empty
 * then a new execution list can be submitted. The two requests at the front of
 * the queue are next to be submitted but since a context may not occur twice in
 * an execution list, if subsequent requests have the same ID as the first then
 * the two requests must be combined. This is done simply by discarding requests
 * at the head of the queue until either only one requests is left (in which case
 * we use a NULL second context) or the first two requests have unique IDs.
 *
 * By always executing the first two requests in the queue the driver ensures
 * that the GPU is kept as busy as possible. In the case where a single context
 * completes but a second context is still executing, the request for this second
 * context will be at the head of the queue when we remove the first one. This
 * request will then be resubmitted along with a new request for a different context,
 * which will cause the hardware to continue executing the second request and queue
 * the new request (the GPU detects the condition of a context getting preempted
 * with the same context and optimizes the context switch flow by not doing
 * preemption, but just sampling the new tail pointer).
 *
 */
#include <linux/interrupt.h>

#include "i915_drv.h"
#include "i915_perf.h"
#include "i915_trace.h"
#include "i915_vgpu.h"
#include "intel_breadcrumbs.h"
#include "intel_context.h"
#include "intel_engine_pm.h"
#include "intel_gt.h"
#include "intel_gt_pm.h"
#include "intel_gt_requests.h"
#include "intel_lrc_reg.h"
#include "intel_mocs.h"
#include "intel_reset.h"
#include "intel_ring.h"
#include "intel_workarounds.h"
#include "shmem_utils.h"

#define RING_EXECLIST_QFULL             (1 << 0x2)
#define RING_EXECLIST1_VALID            (1 << 0x3)
#define RING_EXECLIST0_VALID            (1 << 0x4)
#define RING_EXECLIST_ACTIVE_STATUS     (3 << 0xE)
#define RING_EXECLIST1_ACTIVE           (1 << 0x11)
#define RING_EXECLIST0_ACTIVE           (1 << 0x12)

#define GEN8_CTX_STATUS_IDLE_ACTIVE     (1 << 0)
#define GEN8_CTX_STATUS_PREEMPTED       (1 << 1)
#define GEN8_CTX_STATUS_ELEMENT_SWITCH  (1 << 2)
#define GEN8_CTX_STATUS_ACTIVE_IDLE     (1 << 3)
#define GEN8_CTX_STATUS_COMPLETE        (1 << 4)
#define GEN8_CTX_STATUS_LITE_RESTORE    (1 << 15)

#define GEN8_CTX_STATUS_COMPLETED_MASK \
         (GEN8_CTX_STATUS_COMPLETE | GEN8_CTX_STATUS_PREEMPTED)

#define CTX_DESC_FORCE_RESTORE BIT_ULL(2)

#define GEN12_CTX_STATUS_SWITCHED_TO_NEW_QUEUE  (0x1) /* lower csb dword */
#define GEN12_CTX_SWITCH_DETAIL(csb_dw) ((csb_dw) & 0xF) /* upper csb dword */
#define GEN12_CSB_SW_CTX_ID_MASK                GENMASK(25, 15)
#define GEN12_IDLE_CTX_ID               0x7FF
#define GEN12_CSB_CTX_VALID(csb_dw) \
        (FIELD_GET(GEN12_CSB_SW_CTX_ID_MASK, csb_dw) != GEN12_IDLE_CTX_ID)

/* Typical size of the average request (2 pipecontrols and a MI_BB) */
#define EXECLISTS_REQUEST_SIZE 64 /* bytes */

struct virtual_engine {
        struct intel_engine_cs base;
        struct intel_context context;
        struct rcu_work rcu;

        /*
         * We allow only a single request through the virtual engine at a time
         * (each request in the timeline waits for the completion fence of
         * the previous before being submitted). By restricting ourselves to
         * only submitting a single request, each request is placed on to a
         * physical to maximise load spreading (by virtue of the late greedy
         * scheduling -- each real engine takes the next available request
         * upon idling).
         */
        struct i915_request *request;

        /*
         * We keep a rbtree of available virtual engines inside each physical
         * engine, sorted by priority. Here we preallocate the nodes we need
         * for the virtual engine, indexed by physical_engine->id.
         */
        struct ve_node {
                struct rb_node rb;
                int prio;
        } nodes[I915_NUM_ENGINES];

        /*
         * Keep track of bonded pairs -- restrictions upon on our selection
         * of physical engines any particular request may be submitted to.
         * If we receive a submit-fence from a master engine, we will only
         * use one of sibling_mask physical engines.
         */
        struct ve_bond {
                const struct intel_engine_cs *master;
                intel_engine_mask_t sibling_mask;
        } *bonds;
        unsigned int num_bonds;

        /* And finally, which physical engines this virtual engine maps onto. */
        unsigned int num_siblings;
        struct intel_engine_cs *siblings[];
};

static struct virtual_engine *to_virtual_engine(struct intel_engine_cs *engine)
{
        GEM_BUG_ON(!intel_engine_is_virtual(engine));
        return container_of(engine, struct virtual_engine, base);
}

static int __execlists_context_alloc(struct intel_context *ce,
                                     struct intel_engine_cs *engine);

static void execlists_init_reg_state(u32 *reg_state,
                                     const struct intel_context *ce,
                                     const struct intel_engine_cs *engine,
                                     const struct intel_ring *ring,
                                     bool close);
static void
__execlists_update_reg_state(const struct intel_context *ce,
                             const struct intel_engine_cs *engine,
                             u32 head);

static int lrc_ring_mi_mode(const struct intel_engine_cs *engine)
{
        if (INTEL_GEN(engine->i915) >= 12)
                return 0x60;
        else if (INTEL_GEN(engine->i915) >= 9)
                return 0x54;
        else if (engine->class == RENDER_CLASS)
                return 0x58;
        else
                return -1;
}

static int lrc_ring_gpr0(const struct intel_engine_cs *engine)
{
        if (INTEL_GEN(engine->i915) >= 12)
                return 0x74;
        else if (INTEL_GEN(engine->i915) >= 9)
                return 0x68;
        else if (engine->class == RENDER_CLASS)
                return 0xd8;
        else
                return -1;
}

static int lrc_ring_wa_bb_per_ctx(const struct intel_engine_cs *engine)
{
        if (INTEL_GEN(engine->i915) >= 12)
                return 0x12;
        else if (INTEL_GEN(engine->i915) >= 9 || engine->class == RENDER_CLASS)
                return 0x18;
        else
                return -1;
}

static int lrc_ring_indirect_ptr(const struct intel_engine_cs *engine)
{
        int x;

        x = lrc_ring_wa_bb_per_ctx(engine);
        if (x < 0)
                return x;

        return x + 2;
}

static int lrc_ring_indirect_offset(const struct intel_engine_cs *engine)
{
        int x;

        x = lrc_ring_indirect_ptr(engine);
        if (x < 0)
                return x;

        return x + 2;
}

static int lrc_ring_cmd_buf_cctl(const struct intel_engine_cs *engine)
{
        if (engine->class != RENDER_CLASS)
                return -1;

        if (INTEL_GEN(engine->i915) >= 12)
                return 0xb6;
        else if (INTEL_GEN(engine->i915) >= 11)
                return 0xaa;
        else
                return -1;
}

static u32
lrc_ring_indirect_offset_default(const struct intel_engine_cs *engine)
{
        switch (INTEL_GEN(engine->i915)) {
        default:
                MISSING_CASE(INTEL_GEN(engine->i915));
                fallthrough;
        case 12:
                return GEN12_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
        case 11:
                return GEN11_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
        case 10:
                return GEN10_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
        case 9:
                return GEN9_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
        case 8:
                return GEN8_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
        }
}

static void
lrc_ring_setup_indirect_ctx(u32 *regs,
                            const struct intel_engine_cs *engine,
                            u32 ctx_bb_ggtt_addr,
                            u32 size)
{
        GEM_BUG_ON(!size);
        GEM_BUG_ON(!IS_ALIGNED(size, CACHELINE_BYTES));
        GEM_BUG_ON(lrc_ring_indirect_ptr(engine) == -1);
        regs[lrc_ring_indirect_ptr(engine) + 1] =
                ctx_bb_ggtt_addr | (size / CACHELINE_BYTES);

        GEM_BUG_ON(lrc_ring_indirect_offset(engine) == -1);
        regs[lrc_ring_indirect_offset(engine) + 1] =
                lrc_ring_indirect_offset_default(engine) << 6;
}

static u32 intel_context_get_runtime(const struct intel_context *ce)
{
        /*
         * We can use either ppHWSP[16] which is recorded before the context
         * switch (and so excludes the cost of context switches) or use the
         * value from the context image itself, which is saved/restored earlier
         * and so includes the cost of the save.
         */
        return READ_ONCE(ce->lrc_reg_state[CTX_TIMESTAMP]);
}

static void mark_eio(struct i915_request *rq)
{
        if (i915_request_completed(rq))
                return;

        GEM_BUG_ON(i915_request_signaled(rq));

        i915_request_set_error_once(rq, -EIO);
        i915_request_mark_complete(rq);
}

static struct i915_request *
active_request(const struct intel_timeline * const tl, struct i915_request *rq)
{
        struct i915_request *active = rq;

        rcu_read_lock();
        list_for_each_entry_continue_reverse(rq, &tl->requests, link) {
                if (i915_request_completed(rq))
                        break;

                active = rq;
        }
        rcu_read_unlock();

        return active;
}

static inline u32 intel_hws_preempt_address(struct intel_engine_cs *engine)
{
        return (i915_ggtt_offset(engine->status_page.vma) +
                I915_GEM_HWS_PREEMPT_ADDR);
}

static inline void
ring_set_paused(const struct intel_engine_cs *engine, int state)
{
        /*
         * We inspect HWS_PREEMPT with a semaphore inside
         * engine->emit_fini_breadcrumb. If the dword is true,
         * the ring is paused as the semaphore will busywait
         * until the dword is false.
         */
        engine->status_page.addr[I915_GEM_HWS_PREEMPT] = state;
        if (state)
                wmb();
}

static inline struct i915_priolist *to_priolist(struct rb_node *rb)
{
        return rb_entry(rb, struct i915_priolist, node);
}

static inline int rq_prio(const struct i915_request *rq)
{
        return READ_ONCE(rq->sched.attr.priority);
}

static int effective_prio(const struct i915_request *rq)
{
        int prio = rq_prio(rq);

        /*
         * If this request is special and must not be interrupted at any
         * cost, so be it. Note we are only checking the most recent request
         * in the context and so may be masking an earlier vip request. It
         * is hoped that under the conditions where nopreempt is used, this
         * will not matter (i.e. all requests to that context will be
         * nopreempt for as long as desired).
         */
        if (i915_request_has_nopreempt(rq))
                prio = I915_PRIORITY_UNPREEMPTABLE;

        return prio;
}

static int queue_prio(const struct intel_engine_execlists *execlists)
{
        struct i915_priolist *p;
        struct rb_node *rb;

        rb = rb_first_cached(&execlists->queue);
        if (!rb)
                return INT_MIN;

        /*
         * As the priolist[] are inverted, with the highest priority in [0],
         * we have to flip the index value to become priority.
         */
        p = to_priolist(rb);
        if (!I915_USER_PRIORITY_SHIFT)
                return p->priority;

        return ((p->priority + 1) << I915_USER_PRIORITY_SHIFT) - ffs(p->used);
}

static inline bool need_preempt(const struct intel_engine_cs *engine,
                                const struct i915_request *rq,
                                struct rb_node *rb)
{
        int last_prio;

        if (!intel_engine_has_semaphores(engine))
                return false;

        /*
         * Check if the current priority hint merits a preemption attempt.
         *
         * We record the highest value priority we saw during rescheduling
         * prior to this dequeue, therefore we know that if it is strictly
         * less than the current tail of ESLP[0], we do not need to force
         * a preempt-to-idle cycle.
         *
         * However, the priority hint is a mere hint that we may need to
         * preempt. If that hint is stale or we may be trying to preempt
         * ourselves, ignore the request.
         *
         * More naturally we would write
         *      prio >= max(0, last);
         * except that we wish to prevent triggering preemption at the same
         * priority level: the task that is running should remain running
         * to preserve FIFO ordering of dependencies.
         */
        last_prio = max(effective_prio(rq), I915_PRIORITY_NORMAL - 1);
        if (engine->execlists.queue_priority_hint <= last_prio)
                return false;

        /*
         * Check against the first request in ELSP[1], it will, thanks to the
         * power of PI, be the highest priority of that context.
         */
        if (!list_is_last(&rq->sched.link, &engine->active.requests) &&
            rq_prio(list_next_entry(rq, sched.link)) > last_prio)
                return true;

        if (rb) {
                struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
                bool preempt = false;

                if (engine == ve->siblings[0]) { /* only preempt one sibling */
                        struct i915_request *next;

                        rcu_read_lock();
                        next = READ_ONCE(ve->request);
                        if (next)
                                preempt = rq_prio(next) > last_prio;
                        rcu_read_unlock();
                }

                if (preempt)
                        return preempt;
        }

        /*
         * If the inflight context did not trigger the preemption, then maybe
         * it was the set of queued requests? Pick the highest priority in
         * the queue (the first active priolist) and see if it deserves to be
         * running instead of ELSP[0].
         *
         * The highest priority request in the queue can not be either
         * ELSP[0] or ELSP[1] as, thanks again to PI, if it was the same
         * context, it's priority would not exceed ELSP[0] aka last_prio.
         */
        return queue_prio(&engine->execlists) > last_prio;
}

__maybe_unused static inline bool
assert_priority_queue(const struct i915_request *prev,
                      const struct i915_request *next)
{
        /*
         * Without preemption, the prev may refer to the still active element
         * which we refuse to let go.
         *
         * Even with preemption, there are times when we think it is better not
         * to preempt and leave an ostensibly lower priority request in flight.
         */
        if (i915_request_is_active(prev))
                return true;

        return rq_prio(prev) >= rq_prio(next);
}

/*
 * The context descriptor encodes various attributes of a context,
 * including its GTT address and some flags. Because it's fairly
 * expensive to calculate, we'll just do it once and cache the result,
 * which remains valid until the context is unpinned.
 *
 * This is what a descriptor looks like, from LSB to MSB::
 *
 *      bits  0-11:    flags, GEN8_CTX_* (cached in ctx->desc_template)
 *      bits 12-31:    LRCA, GTT address of (the HWSP of) this context
 *      bits 32-52:    ctx ID, a globally unique tag (highest bit used by GuC)
 *      bits 53-54:    mbz, reserved for use by hardware
 *      bits 55-63:    group ID, currently unused and set to 0
 *
 * Starting from Gen11, the upper dword of the descriptor has a new format:
 *
 *      bits 32-36:    reserved
 *      bits 37-47:    SW context ID
 *      bits 48:53:    engine instance
 *      bit 54:        mbz, reserved for use by hardware
 *      bits 55-60:    SW counter
 *      bits 61-63:    engine class
 *
 * engine info, SW context ID and SW counter need to form a unique number
 * (Context ID) per lrc.
 */
static u32
lrc_descriptor(struct intel_context *ce, struct intel_engine_cs *engine)
{
        u32 desc;

        desc = INTEL_LEGACY_32B_CONTEXT;
        if (i915_vm_is_4lvl(ce->vm))
                desc = INTEL_LEGACY_64B_CONTEXT;
        desc <<= GEN8_CTX_ADDRESSING_MODE_SHIFT;

        desc |= GEN8_CTX_VALID | GEN8_CTX_PRIVILEGE;
        if (IS_GEN(engine->i915, 8))
                desc |= GEN8_CTX_L3LLC_COHERENT;

        return i915_ggtt_offset(ce->state) | desc;
}

static inline unsigned int dword_in_page(void *addr)
{
        return offset_in_page(addr) / sizeof(u32);
}

static void set_offsets(u32 *regs,
                        const u8 *data,
                        const struct intel_engine_cs *engine,
                        bool clear)
#define NOP(x) (BIT(7) | (x))
#define LRI(count, flags) ((flags) << 6 | (count) | BUILD_BUG_ON_ZERO(count >= BIT(6)))
#define POSTED BIT(0)
#define REG(x) (((x) >> 2) | BUILD_BUG_ON_ZERO(x >= 0x200))
#define REG16(x) \
        (((x) >> 9) | BIT(7) | BUILD_BUG_ON_ZERO(x >= 0x10000)), \
        (((x) >> 2) & 0x7f)
#define END(total_state_size) 0, (total_state_size)
{
        const u32 base = engine->mmio_base;

        while (*data) {
                u8 count, flags;

                if (*data & BIT(7)) { /* skip */
                        count = *data++ & ~BIT(7);
                        if (clear)
                                memset32(regs, MI_NOOP, count);
                        regs += count;
                        continue;
                }

                count = *data & 0x3f;
                flags = *data >> 6;
                data++;

                *regs = MI_LOAD_REGISTER_IMM(count);
                if (flags & POSTED)
                        *regs |= MI_LRI_FORCE_POSTED;
                if (INTEL_GEN(engine->i915) >= 11)
                        *regs |= MI_LRI_LRM_CS_MMIO;
                regs++;

                GEM_BUG_ON(!count);
                do {
                        u32 offset = 0;
                        u8 v;

                        do {
                                v = *data++;
                                offset <<= 7;
                                offset |= v & ~BIT(7);
                        } while (v & BIT(7));

                        regs[0] = base + (offset << 2);
                        if (clear)
                                regs[1] = 0;
                        regs += 2;
                } while (--count);
        }

        if (clear) {
                u8 count = *++data;

                /* Clear past the tail for HW access */
                GEM_BUG_ON(dword_in_page(regs) > count);
                memset32(regs, MI_NOOP, count - dword_in_page(regs));

                /* Close the batch; used mainly by live_lrc_layout() */
                *regs = MI_BATCH_BUFFER_END;
                if (INTEL_GEN(engine->i915) >= 10)
                        *regs |= BIT(0);
        }
}

static const u8 gen8_xcs_offsets[] = {
        NOP(1),
        LRI(11, 0),
        REG16(0x244),
        REG(0x034),
        REG(0x030),
        REG(0x038),
        REG(0x03c),
        REG(0x168),
        REG(0x140),
        REG(0x110),
        REG(0x11c),
        REG(0x114),
        REG(0x118),

        NOP(9),
        LRI(9, 0),
        REG16(0x3a8),
        REG16(0x28c),
        REG16(0x288),
        REG16(0x284),
        REG16(0x280),
        REG16(0x27c),
        REG16(0x278),
        REG16(0x274),
        REG16(0x270),

        NOP(13),
        LRI(2, 0),
        REG16(0x200),
        REG(0x028),

        END(80)
};

static const u8 gen9_xcs_offsets[] = {
        NOP(1),
        LRI(14, POSTED),
        REG16(0x244),
        REG(0x034),
        REG(0x030),
        REG(0x038),
        REG(0x03c),
        REG(0x168),
        REG(0x140),
        REG(0x110),
        REG(0x11c),
        REG(0x114),
        REG(0x118),
        REG(0x1c0),
        REG(0x1c4),
        REG(0x1c8),

        NOP(3),
        LRI(9, POSTED),
        REG16(0x3a8),
        REG16(0x28c),
        REG16(0x288),
        REG16(0x284),
        REG16(0x280),
        REG16(0x27c),
        REG16(0x278),
        REG16(0x274),
        REG16(0x270),

        NOP(13),
        LRI(1, POSTED),
        REG16(0x200),

        NOP(13),
        LRI(44, POSTED),
        REG(0x028),
        REG(0x09c),
        REG(0x0c0),
        REG(0x178),
        REG(0x17c),
        REG16(0x358),
        REG(0x170),
        REG(0x150),
        REG(0x154),
        REG(0x158),
        REG16(0x41c),
        REG16(0x600),
        REG16(0x604),
        REG16(0x608),
        REG16(0x60c),
        REG16(0x610),
        REG16(0x614),
        REG16(0x618),
        REG16(0x61c),
        REG16(0x620),
        REG16(0x624),
        REG16(0x628),
        REG16(0x62c),
        REG16(0x630),
        REG16(0x634),
        REG16(0x638),
        REG16(0x63c),
        REG16(0x640),
        REG16(0x644),
        REG16(0x648),
        REG16(0x64c),
        REG16(0x650),
        REG16(0x654),
        REG16(0x658),
        REG16(0x65c),
        REG16(0x660),
        REG16(0x664),
        REG16(0x668),
        REG16(0x66c),
        REG16(0x670),
        REG16(0x674),
        REG16(0x678),
        REG16(0x67c),
        REG(0x068),

        END(176)
};

static const u8 gen12_xcs_offsets[] = {
        NOP(1),
        LRI(13, POSTED),
        REG16(0x244),
        REG(0x034),
        REG(0x030),
        REG(0x038),
        REG(0x03c),
        REG(0x168),
        REG(0x140),
        REG(0x110),
        REG(0x1c0),
        REG(0x1c4),
        REG(0x1c8),
        REG(0x180),
        REG16(0x2b4),

        NOP(5),
        LRI(9, POSTED),
        REG16(0x3a8),
        REG16(0x28c),
        REG16(0x288),
        REG16(0x284),
        REG16(0x280),
        REG16(0x27c),
        REG16(0x278),
        REG16(0x274),
        REG16(0x270),

        END(80)
};

static const u8 gen8_rcs_offsets[] = {
        NOP(1),
        LRI(14, POSTED),
        REG16(0x244),
        REG(0x034),
        REG(0x030),
        REG(0x038),
        REG(0x03c),
        REG(0x168),
        REG(0x140),
        REG(0x110),
        REG(0x11c),
        REG(0x114),
        REG(0x118),
        REG(0x1c0),
        REG(0x1c4),
        REG(0x1c8),

        NOP(3),
        LRI(9, POSTED),
        REG16(0x3a8),
        REG16(0x28c),
        REG16(0x288),
        REG16(0x284),
        REG16(0x280),
        REG16(0x27c),
        REG16(0x278),
        REG16(0x274),
        REG16(0x270),

        NOP(13),
        LRI(1, 0),
        REG(0x0c8),

        END(80)
};

static const u8 gen9_rcs_offsets[] = {
        NOP(1),
        LRI(14, POSTED),
        REG16(0x244),
        REG(0x34),
        REG(0x30),
        REG(0x38),
        REG(0x3c),
        REG(0x168),
        REG(0x140),
        REG(0x110),
        REG(0x11c),
        REG(0x114),
        REG(0x118),
        REG(0x1c0),
        REG(0x1c4),
        REG(0x1c8),

        NOP(3),
        LRI(9, POSTED),
        REG16(0x3a8),
        REG16(0x28c),
        REG16(0x288),
        REG16(0x284),
        REG16(0x280),
        REG16(0x27c),
        REG16(0x278),
        REG16(0x274),
        REG16(0x270),

        NOP(13),
        LRI(1, 0),
        REG(0xc8),

        NOP(13),
        LRI(44, POSTED),
        REG(0x28),
        REG(0x9c),
        REG(0xc0),
        REG(0x178),
        REG(0x17c),
        REG16(0x358),
        REG(0x170),
        REG(0x150),
        REG(0x154),
        REG(0x158),
        REG16(0x41c),
        REG16(0x600),
        REG16(0x604),
        REG16(0x608),
        REG16(0x60c),
        REG16(0x610),
        REG16(0x614),
        REG16(0x618),
        REG16(0x61c),
        REG16(0x620),
        REG16(0x624),
        REG16(0x628),
        REG16(0x62c),
        REG16(0x630),
        REG16(0x634),
        REG16(0x638),
        REG16(0x63c),
        REG16(0x640),
        REG16(0x644),
        REG16(0x648),
        REG16(0x64c),
        REG16(0x650),
        REG16(0x654),
        REG16(0x658),
        REG16(0x65c),
        REG16(0x660),
        REG16(0x664),
        REG16(0x668),
        REG16(0x66c),
        REG16(0x670),
        REG16(0x674),
        REG16(0x678),
        REG16(0x67c),
        REG(0x68),

        END(176)
};

static const u8 gen11_rcs_offsets[] = {
        NOP(1),
        LRI(15, POSTED),
        REG16(0x244),
        REG(0x034),
        REG(0x030),
        REG(0x038),
        REG(0x03c),
        REG(0x168),
        REG(0x140),
        REG(0x110),
        REG(0x11c),
        REG(0x114),
        REG(0x118),
        REG(0x1c0),
        REG(0x1c4),
        REG(0x1c8),
        REG(0x180),

        NOP(1),
        LRI(9, POSTED),
        REG16(0x3a8),
        REG16(0x28c),
        REG16(0x288),
        REG16(0x284),
        REG16(0x280),
        REG16(0x27c),
        REG16(0x278),
        REG16(0x274),
        REG16(0x270),

        LRI(1, POSTED),
        REG(0x1b0),

        NOP(10),
        LRI(1, 0),
        REG(0x0c8),

        END(80)
};

static const u8 gen12_rcs_offsets[] = {
        NOP(1),
        LRI(13, POSTED),
        REG16(0x244),
        REG(0x034),
        REG(0x030),
        REG(0x038),
        REG(0x03c),
        REG(0x168),
        REG(0x140),
        REG(0x110),
        REG(0x1c0),
        REG(0x1c4),
        REG(0x1c8),
        REG(0x180),
        REG16(0x2b4),

        NOP(5),
        LRI(9, POSTED),
        REG16(0x3a8),
        REG16(0x28c),
        REG16(0x288),
        REG16(0x284),
        REG16(0x280),
        REG16(0x27c),
        REG16(0x278),

        REG16(0x274),
        REG16(0x270),

        LRI(3, POSTED),
        REG(0x1b0),
        REG16(0x5a8),
        REG16(0x5ac),

        NOP(6),
        LRI(1, 0),
        REG(0x0c8),
        NOP(3 + 9 + 1),

        LRI(51, POSTED),
        REG16(0x588),
        REG16(0x588),
        REG16(0x588),
        REG16(0x588),
        REG16(0x588),
        REG16(0x588),
        REG(0x028),
        REG(0x09c),
        REG(0x0c0),
        REG(0x178),
        REG(0x17c),
        REG16(0x358),
        REG(0x170),
        REG(0x150),
        REG(0x154),
        REG(0x158),
        REG16(0x41c),
        REG16(0x600),
        REG16(0x604),
        REG16(0x608),
        REG16(0x60c),
        REG16(0x610),
        REG16(0x614),
        REG16(0x618),
        REG16(0x61c),
        REG16(0x620),
        REG16(0x624),
        REG16(0x628),
        REG16(0x62c),
        REG16(0x630),
        REG16(0x634),
        REG16(0x638),
        REG16(0x63c),
        REG16(0x640),
        REG16(0x644),
        REG16(0x648),
        REG16(0x64c),
        REG16(0x650),
        REG16(0x654),
        REG16(0x658),
        REG16(0x65c),
        REG16(0x660),
        REG16(0x664),
        REG16(0x668),
        REG16(0x66c),
        REG16(0x670),
        REG16(0x674),
        REG16(0x678),
        REG16(0x67c),
        REG(0x068),
        REG(0x084),
        NOP(1),

        END(192)
};

#undef END
#undef REG16
#undef REG
#undef LRI
#undef NOP

static const u8 *reg_offsets(const struct intel_engine_cs *engine)
{
        /*
         * The gen12+ lists only have the registers we program in the basic
         * default state. We rely on the context image using relative
         * addressing to automatic fixup the register state between the
         * physical engines for virtual engine.
         */
        GEM_BUG_ON(INTEL_GEN(engine->i915) >= 12 &&
                   !intel_engine_has_relative_mmio(engine));

        if (engine->class == RENDER_CLASS) {
                if (INTEL_GEN(engine->i915) >= 12)
                        return gen12_rcs_offsets;
                else if (INTEL_GEN(engine->i915) >= 11)
                        return gen11_rcs_offsets;
                else if (INTEL_GEN(engine->i915) >= 9)
                        return gen9_rcs_offsets;
                else
                        return gen8_rcs_offsets;
        } else {
                if (INTEL_GEN(engine->i915) >= 12)
                        return gen12_xcs_offsets;
                else if (INTEL_GEN(engine->i915) >= 9)
                        return gen9_xcs_offsets;
                else
                        return gen8_xcs_offsets;
        }
}

static struct i915_request *
__unwind_incomplete_requests(struct intel_engine_cs *engine)
{
        struct i915_request *rq, *rn, *active = NULL;
        struct list_head *pl;
        int prio = I915_PRIORITY_INVALID;

        lockdep_assert_held(&engine->active.lock);

        list_for_each_entry_safe_reverse(rq, rn,
                                         &engine->active.requests,
                                         sched.link) {
                if (i915_request_completed(rq))
                        continue; /* XXX */

                __i915_request_unsubmit(rq);

                /*
                 * Push the request back into the queue for later resubmission.
                 * If this request is not native to this physical engine (i.e.
                 * it came from a virtual source), push it back onto the virtual
                 * engine so that it can be moved across onto another physical
                 * engine as load dictates.
                 */
                if (likely(rq->execution_mask == engine->mask)) {
                        GEM_BUG_ON(rq_prio(rq) == I915_PRIORITY_INVALID);
                        if (rq_prio(rq) != prio) {
                                prio = rq_prio(rq);
                                pl = i915_sched_lookup_priolist(engine, prio);
                        }
                        GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));

                        list_move(&rq->sched.link, pl);
                        set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);

                        /* Check in case we rollback so far we wrap [size/2] */
                        if (intel_ring_direction(rq->ring,
                                                 rq->tail,
                                                 rq->ring->tail + 8) > 0)
                                rq->context->lrc.desc |= CTX_DESC_FORCE_RESTORE;

                        active = rq;
                } else {
                        struct intel_engine_cs *owner = rq->context->engine;

                        WRITE_ONCE(rq->engine, owner);
                        owner->submit_request(rq);
                        active = NULL;
                }
        }

        return active;
}

struct i915_request *
execlists_unwind_incomplete_requests(struct intel_engine_execlists *execlists)
{
        struct intel_engine_cs *engine =
                container_of(execlists, typeof(*engine), execlists);

        return __unwind_incomplete_requests(engine);
}

static inline void
execlists_context_status_change(struct i915_request *rq, unsigned long status)
{
        /*
         * Only used when GVT-g is enabled now. When GVT-g is disabled,
         * The compiler should eliminate this function as dead-code.
         */
        if (!IS_ENABLED(CONFIG_DRM_I915_GVT))
                return;

        atomic_notifier_call_chain(&rq->engine->context_status_notifier,
                                   status, rq);
}

static void intel_engine_context_in(struct intel_engine_cs *engine)
{
        unsigned long flags;

        if (atomic_add_unless(&engine->stats.active, 1, 0))
                return;

        write_seqlock_irqsave(&engine->stats.lock, flags);
        if (!atomic_add_unless(&engine->stats.active, 1, 0)) {
                engine->stats.start = ktime_get();
                atomic_inc(&engine->stats.active);
        }
        write_sequnlock_irqrestore(&engine->stats.lock, flags);
}

static void intel_engine_context_out(struct intel_engine_cs *engine)
{
        unsigned long flags;

        GEM_BUG_ON(!atomic_read(&engine->stats.active));

        if (atomic_add_unless(&engine->stats.active, -1, 1))
                return;

        write_seqlock_irqsave(&engine->stats.lock, flags);
        if (atomic_dec_and_test(&engine->stats.active)) {
                engine->stats.total =
                        ktime_add(engine->stats.total,
                                  ktime_sub(ktime_get(), engine->stats.start));
        }
        write_sequnlock_irqrestore(&engine->stats.lock, flags);
}

static void
execlists_check_context(const struct intel_context *ce,
                        const struct intel_engine_cs *engine)
{
        const struct intel_ring *ring = ce->ring;
        u32 *regs = ce->lrc_reg_state;
        bool valid = true;
        int x;

        if (regs[CTX_RING_START] != i915_ggtt_offset(ring->vma)) {
                pr_err("%s: context submitted with incorrect RING_START [%08x], expected %08x\n",
                       engine->name,
                       regs[CTX_RING_START],
                       i915_ggtt_offset(ring->vma));
                regs[CTX_RING_START] = i915_ggtt_offset(ring->vma);
                valid = false;
        }

        if ((regs[CTX_RING_CTL] & ~(RING_WAIT | RING_WAIT_SEMAPHORE)) !=
            (RING_CTL_SIZE(ring->size) | RING_VALID)) {
                pr_err("%s: context submitted with incorrect RING_CTL [%08x], expected %08x\n",
                       engine->name,
                       regs[CTX_RING_CTL],
                       (u32)(RING_CTL_SIZE(ring->size) | RING_VALID));
                regs[CTX_RING_CTL] = RING_CTL_SIZE(ring->size) | RING_VALID;
                valid = false;
        }

        x = lrc_ring_mi_mode(engine);
        if (x != -1 && regs[x + 1] & (regs[x + 1] >> 16) & STOP_RING) {
                pr_err("%s: context submitted with STOP_RING [%08x] in RING_MI_MODE\n",
                       engine->name, regs[x + 1]);
                regs[x + 1] &= ~STOP_RING;
                regs[x + 1] |= STOP_RING << 16;
                valid = false;
        }

        WARN_ONCE(!valid, "Invalid lrc state found before submission\n");
}

static void restore_default_state(struct intel_context *ce,
                                  struct intel_engine_cs *engine)
{
        u32 *regs;

        regs = memset(ce->lrc_reg_state, 0, engine->context_size - PAGE_SIZE);
        execlists_init_reg_state(regs, ce, engine, ce->ring, true);

        ce->runtime.last = intel_context_get_runtime(ce);
}

static void reset_active(struct i915_request *rq,
                         struct intel_engine_cs *engine)
{
        struct intel_context * const ce = rq->context;
        u32 head;

        /*
         * The executing context has been cancelled. We want to prevent
         * further execution along this context and propagate the error on
         * to anything depending on its results.
         *
         * In __i915_request_submit(), we apply the -EIO and remove the
         * requests' payloads for any banned requests. But first, we must
         * rewind the context back to the start of the incomplete request so
         * that we do not jump back into the middle of the batch.
         *
         * We preserve the breadcrumbs and semaphores of the incomplete
         * requests so that inter-timeline dependencies (i.e other timelines)
         * remain correctly ordered. And we defer to __i915_request_submit()
         * so that all asynchronous waits are correctly handled.
         */
        ENGINE_TRACE(engine, "{ rq=%llx:%lld }\n",
                     rq->fence.context, rq->fence.seqno);

        /* On resubmission of the active request, payload will be scrubbed */
        if (i915_request_completed(rq))
                head = rq->tail;
        else
                head = active_request(ce->timeline, rq)->head;
        head = intel_ring_wrap(ce->ring, head);

        /* Scrub the context image to prevent replaying the previous batch */
        restore_default_state(ce, engine);
        __execlists_update_reg_state(ce, engine, head);

        /* We've switched away, so this should be a no-op, but intent matters */
        ce->lrc.desc |= CTX_DESC_FORCE_RESTORE;
}

static void st_update_runtime_underflow(struct intel_context *ce, s32 dt)
{
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
        ce->runtime.num_underflow += dt < 0;
        ce->runtime.max_underflow = max_t(u32, ce->runtime.max_underflow, -dt);
#endif
}

static void intel_context_update_runtime(struct intel_context *ce)
{
        u32 old;
        s32 dt;

        if (intel_context_is_barrier(ce))
                return;

        old = ce->runtime.last;
        ce->runtime.last = intel_context_get_runtime(ce);
        dt = ce->runtime.last - old;

        if (unlikely(dt <= 0)) {
                CE_TRACE(ce, "runtime underflow: last=%u, new=%u, delta=%d\n",
                         old, ce->runtime.last, dt);
                st_update_runtime_underflow(ce, dt);
                return;
        }

        ewma_runtime_add(&ce->runtime.avg, dt);
        ce->runtime.total += dt;
}

static inline struct intel_engine_cs *
__execlists_schedule_in(struct i915_request *rq)
{
        struct intel_engine_cs * const engine = rq->engine;
        struct intel_context * const ce = rq->context;

        intel_context_get(ce);

        if (unlikely(intel_context_is_banned(ce)))
                reset_active(rq, engine);

        if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
                execlists_check_context(ce, engine);

        if (ce->tag) {
                /* Use a fixed tag for OA and friends */
                GEM_BUG_ON(ce->tag <= BITS_PER_LONG);
                ce->lrc.ccid = ce->tag;
        } else {
                /* We don't need a strict matching tag, just different values */
                unsigned int tag = ffs(READ_ONCE(engine->context_tag));

                GEM_BUG_ON(tag == 0 || tag >= BITS_PER_LONG);
                clear_bit(tag - 1, &engine->context_tag);
                ce->lrc.ccid = tag << (GEN11_SW_CTX_ID_SHIFT - 32);

                BUILD_BUG_ON(BITS_PER_LONG > GEN12_MAX_CONTEXT_HW_ID);
        }

        ce->lrc.ccid |= engine->execlists.ccid;

        __intel_gt_pm_get(engine->gt);
        if (engine->fw_domain && !atomic_fetch_inc(&engine->fw_active))
                intel_uncore_forcewake_get(engine->uncore, engine->fw_domain);
        execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN);
        intel_engine_context_in(engine);

        return engine;
}

static inline struct i915_request *
execlists_schedule_in(struct i915_request *rq, int idx)
{
        struct intel_context * const ce = rq->context;
        struct intel_engine_cs *old;

        GEM_BUG_ON(!intel_engine_pm_is_awake(rq->engine));
        trace_i915_request_in(rq, idx);

        old = READ_ONCE(ce->inflight);
        do {
                if (!old) {
                        WRITE_ONCE(ce->inflight, __execlists_schedule_in(rq));
                        break;
                }
        } while (!try_cmpxchg(&ce->inflight, &old, ptr_inc(old)));

        GEM_BUG_ON(intel_context_inflight(ce) != rq->engine);
        return i915_request_get(rq);
}

static void kick_siblings(struct i915_request *rq, struct intel_context *ce)
{
        struct virtual_engine *ve = container_of(ce, typeof(*ve), context);
        struct i915_request *next = READ_ONCE(ve->request);

        if (next == rq || (next && next->execution_mask & ~rq->execution_mask))
                tasklet_hi_schedule(&ve->base.execlists.tasklet);
}

static inline void
__execlists_schedule_out(struct i915_request *rq,
                         struct intel_engine_cs * const engine,
                         unsigned int ccid)
{
        struct intel_context * const ce = rq->context;

        /*
         * NB process_csb() is not under the engine->active.lock and hence
         * schedule_out can race with schedule_in meaning that we should
         * refrain from doing non-trivial work here.
         */

        /*
         * If we have just completed this context, the engine may now be
         * idle and we want to re-enter powersaving.
         */
        if (list_is_last_rcu(&rq->link, &ce->timeline->requests) &&
            i915_request_completed(rq))
                intel_engine_add_retire(engine, ce->timeline);

        ccid >>= GEN11_SW_CTX_ID_SHIFT - 32;
        ccid &= GEN12_MAX_CONTEXT_HW_ID;
        if (ccid < BITS_PER_LONG) {
                GEM_BUG_ON(ccid == 0);
                GEM_BUG_ON(test_bit(ccid - 1, &engine->context_tag));
                set_bit(ccid - 1, &engine->context_tag);
        }

        intel_context_update_runtime(ce);
        intel_engine_context_out(engine);
        execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_OUT);
        if (engine->fw_domain && !atomic_dec_return(&engine->fw_active))
                intel_uncore_forcewake_put(engine->uncore, engine->fw_domain);
        intel_gt_pm_put_async(engine->gt);

        /*
         * If this is part of a virtual engine, its next request may
         * have been blocked waiting for access to the active context.
         * We have to kick all the siblings again in case we need to
         * switch (e.g. the next request is not runnable on this
         * engine). Hopefully, we will already have submitted the next
         * request before the tasklet runs and do not need to rebuild
         * each virtual tree and kick everyone again.
         */
        if (ce->engine != engine)
                kick_siblings(rq, ce);

        intel_context_put(ce);
}

static inline void
execlists_schedule_out(struct i915_request *rq)
{
        struct intel_context * const ce = rq->context;
        struct intel_engine_cs *cur, *old;
        u32 ccid;

        trace_i915_request_out(rq);

        ccid = rq->context->lrc.ccid;
        old = READ_ONCE(ce->inflight);
        do
                cur = ptr_unmask_bits(old, 2) ? ptr_dec(old) : NULL;
        while (!try_cmpxchg(&ce->inflight, &old, cur));
        if (!cur)
                __execlists_schedule_out(rq, old, ccid);

        i915_request_put(rq);
}

static u64 execlists_update_context(struct i915_request *rq)
{
        struct intel_context *ce = rq->context;
        u64 desc = ce->lrc.desc;
        u32 tail, prev;

        /*
         * WaIdleLiteRestore:bdw,skl
         *
         * We should never submit the context with the same RING_TAIL twice
         * just in case we submit an empty ring, which confuses the HW.
         *
         * We append a couple of NOOPs (gen8_emit_wa_tail) after the end of
         * the normal request to be able to always advance the RING_TAIL on
         * subsequent resubmissions (for lite restore). Should that fail us,
         * and we try and submit the same tail again, force the context
         * reload.
         *
         * If we need to return to a preempted context, we need to skip the
         * lite-restore and force it to reload the RING_TAIL. Otherwise, the
         * HW has a tendency to ignore us rewinding the TAIL to the end of
         * an earlier request.
         */
        GEM_BUG_ON(ce->lrc_reg_state[CTX_RING_TAIL] != rq->ring->tail);
        prev = rq->ring->tail;
        tail = intel_ring_set_tail(rq->ring, rq->tail);
        if (unlikely(intel_ring_direction(rq->ring, tail, prev) <= 0))
                desc |= CTX_DESC_FORCE_RESTORE;
        ce->lrc_reg_state[CTX_RING_TAIL] = tail;
        rq->tail = rq->wa_tail;

        /*
         * Make sure the context image is complete before we submit it to HW.
         *
         * Ostensibly, writes (including the WCB) should be flushed prior to
         * an uncached write such as our mmio register access, the empirical
         * evidence (esp. on Braswell) suggests that the WC write into memory
         * may not be visible to the HW prior to the completion of the UC
         * register write and that we may begin execution from the context
         * before its image is complete leading to invalid PD chasing.
         */
        wmb();

        ce->lrc.desc &= ~CTX_DESC_FORCE_RESTORE;
        return desc;
}

static inline void write_desc(struct intel_engine_execlists *execlists, u64 desc, u32 port)
{
        if (execlists->ctrl_reg) {
                writel(lower_32_bits(desc), execlists->submit_reg + port * 2);
                writel(upper_32_bits(desc), execlists->submit_reg + port * 2 + 1);
        } else {
                writel(upper_32_bits(desc), execlists->submit_reg);
                writel(lower_32_bits(desc), execlists->submit_reg);
        }
}

static __maybe_unused char *
dump_port(char *buf, int buflen, const char *prefix, struct i915_request *rq)
{
        if (!rq)
                return "";

        snprintf(buf, buflen, "%sccid:%x %llx:%lld%s prio %d",
                 prefix,
                 rq->context->lrc.ccid,
                 rq->fence.context, rq->fence.seqno,
                 i915_request_completed(rq) ? "!" :
                 i915_request_started(rq) ? "*" :
                 "",
                 rq_prio(rq));

        return buf;
}

static __maybe_unused void
trace_ports(const struct intel_engine_execlists *execlists,
            const char *msg,
            struct i915_request * const *ports)
{
        const struct intel_engine_cs *engine =
                container_of(execlists, typeof(*engine), execlists);
        char __maybe_unused p0[40], p1[40];

        if (!ports[0])
                return;

        ENGINE_TRACE(engine, "%s { %s%s }\n", msg,
                     dump_port(p0, sizeof(p0), "", ports[0]),
                     dump_port(p1, sizeof(p1), ", ", ports[1]));
}

static inline bool
reset_in_progress(const struct intel_engine_execlists *execlists)
{
        return unlikely(!__tasklet_is_enabled(&execlists->tasklet));
}

static __maybe_unused bool
assert_pending_valid(const struct intel_engine_execlists *execlists,
                     const char *msg)
{
        struct intel_engine_cs *engine =
                container_of(execlists, typeof(*engine), execlists);
        struct i915_request * const *port, *rq;
        struct intel_context *ce = NULL;
        bool sentinel = false;
        u32 ccid = -1;

        trace_ports(execlists, msg, execlists->pending);

        /* We may be messing around with the lists during reset, lalala */
        if (reset_in_progress(execlists))
                return true;

        if (!execlists->pending[0]) {
                GEM_TRACE_ERR("%s: Nothing pending for promotion!\n",
                              engine->name);
                return false;
        }

        if (execlists->pending[execlists_num_ports(execlists)]) {
                GEM_TRACE_ERR("%s: Excess pending[%d] for promotion!\n",
                              engine->name, execlists_num_ports(execlists));
                return false;
        }

        for (port = execlists->pending; (rq = *port); port++) {
                unsigned long flags;
                bool ok = true;

                GEM_BUG_ON(!kref_read(&rq->fence.refcount));
                GEM_BUG_ON(!i915_request_is_active(rq));

                if (ce == rq->context) {
                        GEM_TRACE_ERR("%s: Dup context:%llx in pending[%zd]\n",
                                      engine->name,
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
                        return false;
                }
                ce = rq->context;

                if (ccid == ce->lrc.ccid) {
                        GEM_TRACE_ERR("%s: Dup ccid:%x context:%llx in pending[%zd]\n",
                                      engine->name,
                                      ccid, ce->timeline->fence_context,
                                      port - execlists->pending);
                        return false;
                }
                ccid = ce->lrc.ccid;

                /*
                 * Sentinels are supposed to be the last request so they flush
                 * the current execution off the HW. Check that they are the only
                 * request in the pending submission.
                 */
                if (sentinel) {
                        GEM_TRACE_ERR("%s: context:%llx after sentinel in pending[%zd]\n",
                                      engine->name,
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
                        return false;
                }
                sentinel = i915_request_has_sentinel(rq);

                /* Hold tightly onto the lock to prevent concurrent retires! */
                if (!spin_trylock_irqsave(&rq->lock, flags))
                        continue;

                if (i915_request_completed(rq))
                        goto unlock;

                if (i915_active_is_idle(&ce->active) &&
                    !intel_context_is_barrier(ce)) {
                        GEM_TRACE_ERR("%s: Inactive context:%llx in pending[%zd]\n",
                                      engine->name,
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
                        ok = false;
                        goto unlock;
                }

                if (!i915_vma_is_pinned(ce->state)) {
                        GEM_TRACE_ERR("%s: Unpinned context:%llx in pending[%zd]\n",
                                      engine->name,
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
                        ok = false;
                        goto unlock;
                }

                if (!i915_vma_is_pinned(ce->ring->vma)) {
                        GEM_TRACE_ERR("%s: Unpinned ring:%llx in pending[%zd]\n",
                                      engine->name,
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
                        ok = false;
                        goto unlock;
                }

unlock:
                spin_unlock_irqrestore(&rq->lock, flags);
                if (!ok)
                        return false;
        }

        return ce;
}

static void execlists_submit_ports(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists *execlists = &engine->execlists;
        unsigned int n;

        GEM_BUG_ON(!assert_pending_valid(execlists, "submit"));

        /*
         * We can skip acquiring intel_runtime_pm_get() here as it was taken
         * on our behalf by the request (see i915_gem_mark_busy()) and it will
         * not be relinquished until the device is idle (see
         * i915_gem_idle_work_handler()). As a precaution, we make sure
         * that all ELSP are drained i.e. we have processed the CSB,
         * before allowing ourselves to idle and calling intel_runtime_pm_put().
         */
        GEM_BUG_ON(!intel_engine_pm_is_awake(engine));

        /*
         * ELSQ note: the submit queue is not cleared after being submitted
         * to the HW so we need to make sure we always clean it up. This is
         * currently ensured by the fact that we always write the same number
         * of elsq entries, keep this in mind before changing the loop below.
         */
        for (n = execlists_num_ports(execlists); n--; ) {
                struct i915_request *rq = execlists->pending[n];

                write_desc(execlists,
                           rq ? execlists_update_context(rq) : 0,
                           n);
        }

        /* we need to manually load the submit queue */
        if (execlists->ctrl_reg)
                writel(EL_CTRL_LOAD, execlists->ctrl_reg);
}

static bool ctx_single_port_submission(const struct intel_context *ce)
{
        return (IS_ENABLED(CONFIG_DRM_I915_GVT) &&
                intel_context_force_single_submission(ce));
}

static bool can_merge_ctx(const struct intel_context *prev,
                          const struct intel_context *next)
{
        if (prev != next)
                return false;

        if (ctx_single_port_submission(prev))
                return false;

        return true;
}

static unsigned long i915_request_flags(const struct i915_request *rq)
{
        return READ_ONCE(rq->fence.flags);
}

static bool can_merge_rq(const struct i915_request *prev,
                         const struct i915_request *next)
{
        GEM_BUG_ON(prev == next);
        GEM_BUG_ON(!assert_priority_queue(prev, next));

        /*
         * We do not submit known completed requests. Therefore if the next
         * request is already completed, we can pretend to merge it in
         * with the previous context (and we will skip updating the ELSP
         * and tracking). Thus hopefully keeping the ELSP full with active
         * contexts, despite the best efforts of preempt-to-busy to confuse
         * us.
         */
        if (i915_request_completed(next))
                return true;

        if (unlikely((i915_request_flags(prev) ^ i915_request_flags(next)) &
                     (BIT(I915_FENCE_FLAG_NOPREEMPT) |
                      BIT(I915_FENCE_FLAG_SENTINEL))))
                return false;

        if (!can_merge_ctx(prev->context, next->context))
                return false;

        GEM_BUG_ON(i915_seqno_passed(prev->fence.seqno, next->fence.seqno));
        return true;
}

static void virtual_update_register_offsets(u32 *regs,
                                            struct intel_engine_cs *engine)
{
        set_offsets(regs, reg_offsets(engine), engine, false);
}

static bool virtual_matches(const struct virtual_engine *ve,
                            const struct i915_request *rq,
                            const struct intel_engine_cs *engine)
{
        const struct intel_engine_cs *inflight;

        if (!(rq->execution_mask & engine->mask)) /* We peeked too soon! */
                return false;

        /*
         * We track when the HW has completed saving the context image
         * (i.e. when we have seen the final CS event switching out of
         * the context) and must not overwrite the context image before
         * then. This restricts us to only using the active engine
         * while the previous virtualized request is inflight (so
         * we reuse the register offsets). This is a very small
         * hystersis on the greedy seelction algorithm.
         */
        inflight = intel_context_inflight(&ve->context);
        if (inflight && inflight != engine)
                return false;

        return true;
}

static void virtual_xfer_context(struct virtual_engine *ve,
                                 struct intel_engine_cs *engine)
{
        unsigned int n;

        if (likely(engine == ve->siblings[0]))
                return;

        GEM_BUG_ON(READ_ONCE(ve->context.inflight));
        if (!intel_engine_has_relative_mmio(engine))
                virtual_update_register_offsets(ve->context.lrc_reg_state,
                                                engine);

        /*
         * Move the bound engine to the top of the list for
         * future execution. We then kick this tasklet first
         * before checking others, so that we preferentially
         * reuse this set of bound registers.
         */
        for (n = 1; n < ve->num_siblings; n++) {
                if (ve->siblings[n] == engine) {
                        swap(ve->siblings[n], ve->siblings[0]);
                        break;
                }
        }
}

#define for_each_waiter(p__, rq__) \
        list_for_each_entry_lockless(p__, \
                                     &(rq__)->sched.waiters_list, \
                                     wait_link)

#define for_each_signaler(p__, rq__) \
        list_for_each_entry_rcu(p__, \
                                &(rq__)->sched.signalers_list, \
                                signal_link)

static void defer_request(struct i915_request *rq, struct list_head * const pl)
{
        LIST_HEAD(list);

        /*
         * We want to move the interrupted request to the back of
         * the round-robin list (i.e. its priority level), but
         * in doing so, we must then move all requests that were in
         * flight and were waiting for the interrupted request to
         * be run after it again.
         */
        do {
                struct i915_dependency *p;

                GEM_BUG_ON(i915_request_is_active(rq));
                list_move_tail(&rq->sched.link, pl);

                for_each_waiter(p, rq) {
                        struct i915_request *w =
                                container_of(p->waiter, typeof(*w), sched);

                        if (p->flags & I915_DEPENDENCY_WEAK)
                                continue;

                        /* Leave semaphores spinning on the other engines */
                        if (w->engine != rq->engine)
                                continue;

                        /* No waiter should start before its signaler */
                        GEM_BUG_ON(i915_request_has_initial_breadcrumb(w) &&
                                   i915_request_started(w) &&
                                   !i915_request_completed(rq));

                        GEM_BUG_ON(i915_request_is_active(w));
                        if (!i915_request_is_ready(w))
                                continue;

                        if (rq_prio(w) < rq_prio(rq))
                                continue;

                        GEM_BUG_ON(rq_prio(w) > rq_prio(rq));
                        list_move_tail(&w->sched.link, &list);
                }

                rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
        } while (rq);
}

static void defer_active(struct intel_engine_cs *engine)
{
        struct i915_request *rq;

        rq = __unwind_incomplete_requests(engine);
        if (!rq)
                return;

        defer_request(rq, i915_sched_lookup_priolist(engine, rq_prio(rq)));
}

static bool
need_timeslice(const struct intel_engine_cs *engine,
               const struct i915_request *rq,
               const struct rb_node *rb)
{
        int hint;

        if (!intel_engine_has_timeslices(engine))
                return false;

        hint = engine->execlists.queue_priority_hint;

        if (rb) {
                const struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
                const struct intel_engine_cs *inflight =
                        intel_context_inflight(&ve->context);

                if (!inflight || inflight == engine) {
                        struct i915_request *next;

                        rcu_read_lock();
                        next = READ_ONCE(ve->request);
                        if (next)
                                hint = max(hint, rq_prio(next));
                        rcu_read_unlock();
                }
        }

        if (!list_is_last(&rq->sched.link, &engine->active.requests))
                hint = max(hint, rq_prio(list_next_entry(rq, sched.link)));

        GEM_BUG_ON(hint >= I915_PRIORITY_UNPREEMPTABLE);
        return hint >= effective_prio(rq);
}

static bool
timeslice_yield(const struct intel_engine_execlists *el,
                const struct i915_request *rq)
{
        /*
         * Once bitten, forever smitten!
         *
         * If the active context ever busy-waited on a semaphore,
         * it will be treated as a hog until the end of its timeslice (i.e.
         * until it is scheduled out and replaced by a new submission,
         * possibly even its own lite-restore). The HW only sends an interrupt
         * on the first miss, and we do know if that semaphore has been
         * signaled, or even if it is now stuck on another semaphore. Play
         * safe, yield if it might be stuck -- it will be given a fresh
         * timeslice in the near future.
         */
        return rq->context->lrc.ccid == READ_ONCE(el->yield);
}

static bool
timeslice_expired(const struct intel_engine_execlists *el,
                  const struct i915_request *rq)
{
        return timer_expired(&el->timer) || timeslice_yield(el, rq);
}

static int
switch_prio(struct intel_engine_cs *engine, const struct i915_request *rq)
{
        if (list_is_last(&rq->sched.link, &engine->active.requests))
                return engine->execlists.queue_priority_hint;

        return rq_prio(list_next_entry(rq, sched.link));
}

static inline unsigned long
timeslice(const struct intel_engine_cs *engine)
{
        return READ_ONCE(engine->props.timeslice_duration_ms);
}

static unsigned long active_timeslice(const struct intel_engine_cs *engine)
{
        const struct intel_engine_execlists *execlists = &engine->execlists;
        const struct i915_request *rq = *execlists->active;

        if (!rq || i915_request_completed(rq))
                return 0;

        if (READ_ONCE(execlists->switch_priority_hint) < effective_prio(rq))
                return 0;

        return timeslice(engine);
}

static void set_timeslice(struct intel_engine_cs *engine)
{
        unsigned long duration;

        if (!intel_engine_has_timeslices(engine))

                return;

        duration = active_timeslice(engine);
        ENGINE_TRACE(engine, "bump timeslicing, interval:%lu", duration);

        set_timer_ms(&engine->execlists.timer, duration);
}

static void start_timeslice(struct intel_engine_cs *engine, int prio)
{
        struct intel_engine_execlists *execlists = &engine->execlists;
        unsigned long duration;

        if (!intel_engine_has_timeslices(engine))
                return;

        WRITE_ONCE(execlists->switch_priority_hint, prio);
        if (prio == INT_MIN)
                return;

        if (timer_pending(&execlists->timer))
                return;

        duration = timeslice(engine);
        ENGINE_TRACE(engine,
                     "start timeslicing, prio:%d, interval:%lu",
                     prio, duration);

        set_timer_ms(&execlists->timer, duration);
}

static void record_preemption(struct intel_engine_execlists *execlists)
{
        (void)I915_SELFTEST_ONLY(execlists->preempt_hang.count++);
}

static unsigned long active_preempt_timeout(struct intel_engine_cs *engine,
                                            const struct i915_request *rq)
{
        if (!rq)
                return 0;

        /* Force a fast reset for terminated contexts (ignoring sysfs!) */
        if (unlikely(intel_context_is_banned(rq->context)))
                return 1;

        return READ_ONCE(engine->props.preempt_timeout_ms);
}

static void set_preempt_timeout(struct intel_engine_cs *engine,
                                const struct i915_request *rq)
{
        if (!intel_engine_has_preempt_reset(engine))
                return;

        set_timer_ms(&engine->execlists.preempt,
                     active_preempt_timeout(engine, rq));
}

static inline void clear_ports(struct i915_request **ports, int count)
{
        memset_p((void **)ports, NULL, count);
}

static inline void
copy_ports(struct i915_request **dst, struct i915_request **src, int count)
{
        /* A memcpy_p() would be very useful here! */
        while (count--)
                WRITE_ONCE(*dst++, *src++); /* avoid write tearing */
}

static void execlists_dequeue(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        struct i915_request **port = execlists->pending;
        struct i915_request ** const last_port = port + execlists->port_mask;
        struct i915_request * const *active;
        struct i915_request *last;
        struct rb_node *rb;
        bool submit = false;

        /*
         * Hardware submission is through 2 ports. Conceptually each port
         * has a (RING_START, RING_HEAD, RING_TAIL) tuple. RING_START is
         * static for a context, and unique to each, so we only execute
         * requests belonging to a single context from each ring. RING_HEAD
         * is maintained by the CS in the context image, it marks the place
         * where it got up to last time, and through RING_TAIL we tell the CS
         * where we want to execute up to this time.
         *
         * In this list the requests are in order of execution. Consecutive
         * requests from the same context are adjacent in the ringbuffer. We
         * can combine these requests into a single RING_TAIL update:
         *
         *              RING_HEAD...req1...req2
         *                                    ^- RING_TAIL
         * since to execute req2 the CS must first execute req1.
         *
         * Our goal then is to point each port to the end of a consecutive
         * sequence of requests as being the most optimal (fewest wake ups
         * and context switches) submission.
         */

        for (rb = rb_first_cached(&execlists->virtual); rb; ) {
                struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
                struct i915_request *rq = READ_ONCE(ve->request);

                if (!rq) { /* lazily cleanup after another engine handled rq */
                        rb_erase_cached(rb, &execlists->virtual);
                        RB_CLEAR_NODE(rb);
                        rb = rb_first_cached(&execlists->virtual);
                        continue;
                }

                if (!virtual_matches(ve, rq, engine)) {
                        rb = rb_next(rb);
                        continue;
                }

                break;
        }

        /*
         * If the queue is higher priority than the last
         * request in the currently active context, submit afresh.
         * We will resubmit again afterwards in case we need to split
         * the active context to interject the preemption request,
         * i.e. we will retrigger preemption following the ack in case
         * of trouble.
         */
        active = READ_ONCE(execlists->active);

        /*
         * In theory we can skip over completed contexts that have not
         * yet been processed by events (as those events are in flight):
         *
         * while ((last = *active) && i915_request_completed(last))
         *      active++;
         *
         * However, the GPU cannot handle this as it will ultimately
         * find itself trying to jump back into a context it has just
         * completed and barf.
         */

        if ((last = *active)) {
                if (need_preempt(engine, last, rb)) {
                        if (i915_request_completed(last)) {
                                tasklet_hi_schedule(&execlists->tasklet);
                                return;
                        }

                        ENGINE_TRACE(engine,
                                     "preempting last=%llx:%lld, prio=%d, hint=%d\n",
                                     last->fence.context,
                                     last->fence.seqno,
                                     last->sched.attr.priority,
                                     execlists->queue_priority_hint);
                        record_preemption(execlists);

                        /*
                         * Don't let the RING_HEAD advance past the breadcrumb
                         * as we unwind (and until we resubmit) so that we do
                         * not accidentally tell it to go backwards.
                         */
                        ring_set_paused(engine, 1);

                        /*
                         * Note that we have not stopped the GPU at this point,
                         * so we are unwinding the incomplete requests as they
                         * remain inflight and so by the time we do complete
                         * the preemption, some of the unwound requests may
                         * complete!
                         */
                        __unwind_incomplete_requests(engine);

                        last = NULL;
                } else if (need_timeslice(engine, last, rb) &&
                           timeslice_expired(execlists, last)) {
                        if (i915_request_completed(last)) {
                                tasklet_hi_schedule(&execlists->tasklet);
                                return;
                        }

                        ENGINE_TRACE(engine,
                                     "expired last=%llx:%lld, prio=%d, hint=%d, yield?=%s\n",
                                     last->fence.context,
                                     last->fence.seqno,
                                     last->sched.attr.priority,
                                     execlists->queue_priority_hint,
                                     yesno(timeslice_yield(execlists, last)));

                        ring_set_paused(engine, 1);
                        defer_active(engine);

                        /*
                         * Unlike for preemption, if we rewind and continue
                         * executing the same context as previously active,
                         * the order of execution will remain the same and
                         * the tail will only advance. We do not need to
                         * force a full context restore, as a lite-restore
                         * is sufficient to resample the monotonic TAIL.
                         *
                         * If we switch to any other context, similarly we
                         * will not rewind TAIL of current context, and
                         * normal save/restore will preserve state and allow
                         * us to later continue executing the same request.
                         */
                        last = NULL;
                } else {
                        /*
                         * Otherwise if we already have a request pending
                         * for execution after the current one, we can
                         * just wait until the next CS event before
                         * queuing more. In either case we will force a
                         * lite-restore preemption event, but if we wait
                         * we hopefully coalesce several updates into a single
                         * submission.
                         */
                        if (!list_is_last(&last->sched.link,
                                          &engine->active.requests)) {
                                /*
                                 * Even if ELSP[1] is occupied and not worthy
                                 * of timeslices, our queue might be.
                                 */
                                start_timeslice(engine, queue_prio(execlists));
                                return;
                        }
                }
        }

        while (rb) { /* XXX virtual is always taking precedence */
                struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
                struct i915_request *rq;

                spin_lock(&ve->base.active.lock);

                rq = ve->request;
                if (unlikely(!rq)) { /* lost the race to a sibling */
                        spin_unlock(&ve->base.active.lock);
                        rb_erase_cached(rb, &execlists->virtual);
                        RB_CLEAR_NODE(rb);
                        rb = rb_first_cached(&execlists->virtual);
                        continue;
                }

                GEM_BUG_ON(rq != ve->request);
                GEM_BUG_ON(rq->engine != &ve->base);
                GEM_BUG_ON(rq->context != &ve->context);

                if (rq_prio(rq) >= queue_prio(execlists)) {
                        if (!virtual_matches(ve, rq, engine)) {
                                spin_unlock(&ve->base.active.lock);
                                rb = rb_next(rb);
                                continue;
                        }

                        if (last && !can_merge_rq(last, rq)) {
                                spin_unlock(&ve->base.active.lock);
                                start_timeslice(engine, rq_prio(rq));
                                return; /* leave this for another sibling */
                        }

                        ENGINE_TRACE(engine,
                                     "virtual rq=%llx:%lld%s, new engine? %s\n",
                                     rq->fence.context,
                                     rq->fence.seqno,
                                     i915_request_completed(rq) ? "!" :
                                     i915_request_started(rq) ? "*" :
                                     "",
                                     yesno(engine != ve->siblings[0]));

                        WRITE_ONCE(ve->request, NULL);
                        WRITE_ONCE(ve->base.execlists.queue_priority_hint,
                                   INT_MIN);
                        rb_erase_cached(rb, &execlists->virtual);
                        RB_CLEAR_NODE(rb);

                        GEM_BUG_ON(!(rq->execution_mask & engine->mask));
                        WRITE_ONCE(rq->engine, engine);

                        if (__i915_request_submit(rq)) {
                                /*
                                 * Only after we confirm that we will submit
                                 * this request (i.e. it has not already
                                 * completed), do we want to update the context.
                                 *
                                 * This serves two purposes. It avoids
                                 * unnecessary work if we are resubmitting an
                                 * already completed request after timeslicing.
                                 * But more importantly, it prevents us altering
                                 * ve->siblings[] on an idle context, where
                                 * we may be using ve->siblings[] in
                                 * virtual_context_enter / virtual_context_exit.
                                 */
                                virtual_xfer_context(ve, engine);
                                GEM_BUG_ON(ve->siblings[0] != engine);

                                submit = true;
                                last = rq;
                        }
                        i915_request_put(rq);

                        /*
                         * Hmm, we have a bunch of virtual engine requests,
                         * but the first one was already completed (thanks
                         * preempt-to-busy!). Keep looking at the veng queue
                         * until we have no more relevant requests (i.e.
                         * the normal submit queue has higher priority).
                         */
                        if (!submit) {
                                spin_unlock(&ve->base.active.lock);
                                rb = rb_first_cached(&execlists->virtual);
                                continue;
                        }
                }

                spin_unlock(&ve->base.active.lock);
                break;
        }

        while ((rb = rb_first_cached(&execlists->queue))) {
                struct i915_priolist *p = to_priolist(rb);
                struct i915_request *rq, *rn;
                int i;

                priolist_for_each_request_consume(rq, rn, p, i) {
                        bool merge = true;

                        /*
                         * Can we combine this request with the current port?
                         * It has to be the same context/ringbuffer and not
                         * have any exceptions (e.g. GVT saying never to
                         * combine contexts).
                         *
                         * If we can combine the requests, we can execute both
                         * by updating the RING_TAIL to point to the end of the
                         * second request, and so we never need to tell the
                         * hardware about the first.
                         */
                        if (last && !can_merge_rq(last, rq)) {
                                /*
                                 * If we are on the second port and cannot
                                 * combine this request with the last, then we
                                 * are done.
                                 */
                                if (port == last_port)
                                        goto done;

                                /*
                                 * We must not populate both ELSP[] with the
                                 * same LRCA, i.e. we must submit 2 different
                                 * contexts if we submit 2 ELSP.
                                 */
                                if (last->context == rq->context)
                                        goto done;

                                if (i915_request_has_sentinel(last))
                                        goto done;

                                /*
                                 * If GVT overrides us we only ever submit
                                 * port[0], leaving port[1] empty. Note that we
                                 * also have to be careful that we don't queue
                                 * the same context (even though a different
                                 * request) to the second port.
                                 */
                                if (ctx_single_port_submission(last->context) ||
                                    ctx_single_port_submission(rq->context))
                                        goto done;

                                merge = false;
                        }

                        if (__i915_request_submit(rq)) {
                                if (!merge) {
                                        *port = execlists_schedule_in(last, port - execlists->pending);
                                        port++;
                                        last = NULL;
                                }

                                GEM_BUG_ON(last &&
                                           !can_merge_ctx(last->context,
                                                          rq->context));
                                GEM_BUG_ON(last &&
                                           i915_seqno_passed(last->fence.seqno,
                                                             rq->fence.seqno));

                                submit = true;
                                last = rq;
                        }
                }

                rb_erase_cached(&p->node, &execlists->queue);
                i915_priolist_free(p);
        }

done:
        /*
         * Here be a bit of magic! Or sleight-of-hand, whichever you prefer.
         *
         * We choose the priority hint such that if we add a request of greater
         * priority than this, we kick the submission tasklet to decide on
         * the right order of submitting the requests to hardware. We must
         * also be prepared to reorder requests as they are in-flight on the
         * HW. We derive the priority hint then as the first "hole" in
         * the HW submission ports and if there are no available slots,
         * the priority of the lowest executing request, i.e. last.
         *
         * When we do receive a higher priority request ready to run from the
         * user, see queue_request(), the priority hint is bumped to that
         * request triggering preemption on the next dequeue (or subsequent
         * interrupt for secondary ports).
         */
        execlists->queue_priority_hint = queue_prio(execlists);

        if (submit) {
                *port = execlists_schedule_in(last, port - execlists->pending);
                execlists->switch_priority_hint =
                        switch_prio(engine, *execlists->pending);

                /*
                 * Skip if we ended up with exactly the same set of requests,
                 * e.g. trying to timeslice a pair of ordered contexts
                 */
                if (!memcmp(active, execlists->pending,
                            (port - execlists->pending + 1) * sizeof(*port))) {
                        do
                                execlists_schedule_out(fetch_and_zero(port));
                        while (port-- != execlists->pending);

                        goto skip_submit;
                }
                clear_ports(port + 1, last_port - port);

                WRITE_ONCE(execlists->yield, -1);
                set_preempt_timeout(engine, *active);
                execlists_submit_ports(engine);
        } else {
                start_timeslice(engine, execlists->queue_priority_hint);
skip_submit:
                ring_set_paused(engine, 0);
        }
}

static void
cancel_port_requests(struct intel_engine_execlists * const execlists)
{
        struct i915_request * const *port;

        for (port = execlists->pending; *port; port++)
                execlists_schedule_out(*port);
        clear_ports(execlists->pending, ARRAY_SIZE(execlists->pending));

        /* Mark the end of active before we overwrite *active */
        for (port = xchg(&execlists->active, execlists->pending); *port; port++)
                execlists_schedule_out(*port);
        clear_ports(execlists->inflight, ARRAY_SIZE(execlists->inflight));

        smp_wmb(); /* complete the seqlock for execlists_active() */
        WRITE_ONCE(execlists->active, execlists->inflight);
}

static inline void
invalidate_csb_entries(const u64 *first, const u64 *last)
{
        clflush((void *)first);
        clflush((void *)last);
}

/*
 * Starting with Gen12, the status has a new format:
 *
 *     bit  0:     switched to new queue
 *     bit  1:     reserved
 *     bit  2:     semaphore wait mode (poll or signal), only valid when
 *                 switch detail is set to "wait on semaphore"
 *     bits 3-5:   engine class
 *     bits 6-11:  engine instance
 *     bits 12-14: reserved
 *     bits 15-25: sw context id of the lrc the GT switched to
 *     bits 26-31: sw counter of the lrc the GT switched to
 *     bits 32-35: context switch detail
 *                  - 0: ctx complete
 *                  - 1: wait on sync flip
 *                  - 2: wait on vblank
 *                  - 3: wait on scanline
 *                  - 4: wait on semaphore
 *                  - 5: context preempted (not on SEMAPHORE_WAIT or
 *                       WAIT_FOR_EVENT)
 *     bit  36:    reserved
 *     bits 37-43: wait detail (for switch detail 1 to 4)
 *     bits 44-46: reserved
 *     bits 47-57: sw context id of the lrc the GT switched away from
 *     bits 58-63: sw counter of the lrc the GT switched away from
 */
static inline bool gen12_csb_parse(const u64 *csb)
{
        bool ctx_away_valid;
        bool new_queue;
        u64 entry;

        /* HSD#22011248461 */
        entry = READ_ONCE(*csb);
        if (unlikely(entry == -1)) {
                preempt_disable();
                if (wait_for_atomic_us((entry = READ_ONCE(*csb)) != -1, 50))
                        GEM_WARN_ON("50us CSB timeout");
                preempt_enable();
        }
        WRITE_ONCE(*(u64 *)csb, -1);

        ctx_away_valid = GEN12_CSB_CTX_VALID(upper_32_bits(entry));
        new_queue =
                lower_32_bits(entry) & GEN12_CTX_STATUS_SWITCHED_TO_NEW_QUEUE;

        /*
         * The context switch detail is not guaranteed to be 5 when a preemption
         * occurs, so we can't just check for that. The check below works for
         * all the cases we care about, including preemptions of WAIT
         * instructions and lite-restore. Preempt-to-idle via the CTRL register
         * would require some extra handling, but we don't support that.
         */
        if (!ctx_away_valid || new_queue) {
                GEM_BUG_ON(!GEN12_CSB_CTX_VALID(lower_32_bits(entry)));
                return true;
        }

        /*
         * switch detail = 5 is covered by the case above and we do not expect a
         * context switch on an unsuccessful wait instruction since we always
         * use polling mode.
         */
        GEM_BUG_ON(GEN12_CTX_SWITCH_DETAIL(upper_32_bits(entry)));
        return false;
}

static inline bool gen8_csb_parse(const u64 *csb)
{
        return *csb & (GEN8_CTX_STATUS_IDLE_ACTIVE | GEN8_CTX_STATUS_PREEMPTED);
}

static void process_csb(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        const u64 * const buf = execlists->csb_status;
        const u8 num_entries = execlists->csb_size;
        u8 head, tail;

        /*
         * As we modify our execlists state tracking we require exclusive
         * access. Either we are inside the tasklet, or the tasklet is disabled
         * and we assume that is only inside the reset paths and so serialised.
         */
        GEM_BUG_ON(!tasklet_is_locked(&execlists->tasklet) &&
                   !reset_in_progress(execlists));
        GEM_BUG_ON(!intel_engine_in_execlists_submission_mode(engine));

        /*
         * Note that csb_write, csb_status may be either in HWSP or mmio.
         * When reading from the csb_write mmio register, we have to be
         * careful to only use the GEN8_CSB_WRITE_PTR portion, which is
         * the low 4bits. As it happens we know the next 4bits are always
         * zero and so we can simply masked off the low u8 of the register
         * and treat it identically to reading from the HWSP (without having
         * to use explicit shifting and masking, and probably bifurcating
         * the code to handle the legacy mmio read).
         */
        head = execlists->csb_head;
        tail = READ_ONCE(*execlists->csb_write);
        if (unlikely(head == tail))
                return;

        /*
         * We will consume all events from HW, or at least pretend to.
         *
         * The sequence of events from the HW is deterministic, and derived
         * from our writes to the ELSP, with a smidgen of variability for
         * the arrival of the asynchronous requests wrt to the inflight
         * execution. If the HW sends an event that does not correspond with
         * the one we are expecting, we have to abandon all hope as we lose
         * all tracking of what the engine is actually executing. We will
         * only detect we are out of sequence with the HW when we get an
         * 'impossible' event because we have already drained our own
         * preemption/promotion queue. If this occurs, we know that we likely
         * lost track of execution earlier and must unwind and restart, the
         * simplest way is by stop processing the event queue and force the
         * engine to reset.
         */
        execlists->csb_head = tail;
        ENGINE_TRACE(engine, "cs-irq head=%d, tail=%d\n", head, tail);

        /*
         * Hopefully paired with a wmb() in HW!
         *
         * We must complete the read of the write pointer before any reads
         * from the CSB, so that we do not see stale values. Without an rmb
         * (lfence) the HW may speculatively perform the CSB[] reads *before*
         * we perform the READ_ONCE(*csb_write).
         */
        rmb();
        do {
                bool promote;

                if (++head == num_entries)
                        head = 0;

                /*
                 * We are flying near dragons again.
                 *
                 * We hold a reference to the request in execlist_port[]
                 * but no more than that. We are operating in softirq
                 * context and so cannot hold any mutex or sleep. That
                 * prevents us stopping the requests we are processing
                 * in port[] from being retired simultaneously (the
                 * breadcrumb will be complete before we see the
                 * context-switch). As we only hold the reference to the
                 * request, any pointer chasing underneath the request
                 * is subject to a potential use-after-free. Thus we
                 * store all of the bookkeeping within port[] as
                 * required, and avoid using unguarded pointers beneath
                 * request itself. The same applies to the atomic
                 * status notifier.
                 */

                ENGINE_TRACE(engine, "csb[%d]: status=0x%08x:0x%08x\n",
                             head,
                             upper_32_bits(buf[head]),
                             lower_32_bits(buf[head]));

                if (INTEL_GEN(engine->i915) >= 12)
                        promote = gen12_csb_parse(buf + head);
                else
                        promote = gen8_csb_parse(buf + head);
                if (promote) {
                        struct i915_request * const *old = execlists->active;

                        if (GEM_WARN_ON(!*execlists->pending)) {
                                execlists->error_interrupt |= ERROR_CSB;
                                break;
                        }

                        ring_set_paused(engine, 0);

                        /* Point active to the new ELSP; prevent overwriting */
                        WRITE_ONCE(execlists->active, execlists->pending);
                        smp_wmb(); /* notify execlists_active() */

                        /* cancel old inflight, prepare for switch */
                        trace_ports(execlists, "preempted", old);
                        while (*old)
                                execlists_schedule_out(*old++);

                        /* switch pending to inflight */
                        GEM_BUG_ON(!assert_pending_valid(execlists, "promote"));
                        copy_ports(execlists->inflight,
                                   execlists->pending,
                                   execlists_num_ports(execlists));
                        smp_wmb(); /* complete the seqlock */
                        WRITE_ONCE(execlists->active, execlists->inflight);

                        /* XXX Magic delay for tgl */
                        ENGINE_POSTING_READ(engine, RING_CONTEXT_STATUS_PTR);

                        WRITE_ONCE(execlists->pending[0], NULL);
                } else {
                        if (GEM_WARN_ON(!*execlists->active)) {
                                execlists->error_interrupt |= ERROR_CSB;
                                break;
                        }

                        /* port0 completed, advanced to port1 */
                        trace_ports(execlists, "completed", execlists->active);

                        /*
                         * We rely on the hardware being strongly
                         * ordered, that the breadcrumb write is
                         * coherent (visible from the CPU) before the
                         * user interrupt is processed. One might assume
                         * that the breadcrumb write being before the
                         * user interrupt and the CS event for the context
                         * switch would therefore be before the CS event
                         * itself...
                         */
                        if (GEM_SHOW_DEBUG() &&
                            !i915_request_completed(*execlists->active)) {
                                struct i915_request *rq = *execlists->active;
                                const u32 *regs __maybe_unused =
                                        rq->context->lrc_reg_state;

                                ENGINE_TRACE(engine,
                                             "context completed before request!\n");
                                ENGINE_TRACE(engine,
                                             "ring:{start:0x%08x, head:%04x, tail:%04x, ctl:%08x, mode:%08x}\n",
                                             ENGINE_READ(engine, RING_START),
                                             ENGINE_READ(engine, RING_HEAD) & HEAD_ADDR,
                                             ENGINE_READ(engine, RING_TAIL) & TAIL_ADDR,
                                             ENGINE_READ(engine, RING_CTL),
                                             ENGINE_READ(engine, RING_MI_MODE));
                                ENGINE_TRACE(engine,
                                             "rq:{start:%08x, head:%04x, tail:%04x, seqno:%llx:%d, hwsp:%d}, ",
                                             i915_ggtt_offset(rq->ring->vma),
                                             rq->head, rq->tail,
                                             rq->fence.context,
                                             lower_32_bits(rq->fence.seqno),
                                             hwsp_seqno(rq));
                                ENGINE_TRACE(engine,
                                             "ctx:{start:%08x, head:%04x, tail:%04x}, ",
                                             regs[CTX_RING_START],
                                             regs[CTX_RING_HEAD],
                                             regs[CTX_RING_TAIL]);
                        }

                        execlists_schedule_out(*execlists->active++);

                        GEM_BUG_ON(execlists->active - execlists->inflight >
                                   execlists_num_ports(execlists));
                }
        } while (head != tail);

        set_timeslice(engine);

        /*
         * Gen11 has proven to fail wrt global observation point between
         * entry and tail update, failing on the ordering and thus
         * we see an old entry in the context status buffer.
         *
         * Forcibly evict out entries for the next gpu csb update,
         * to increase the odds that we get a fresh entries with non
         * working hardware. The cost for doing so comes out mostly with
         * the wash as hardware, working or not, will need to do the
         * invalidation before.
         */
        invalidate_csb_entries(&buf[0], &buf[num_entries - 1]);
}

static void __execlists_submission_tasklet(struct intel_engine_cs *const engine)
{
        lockdep_assert_held(&engine->active.lock);
        if (!READ_ONCE(engine->execlists.pending[0])) {
                rcu_read_lock(); /* protect peeking at execlists->active */
                execlists_dequeue(engine);
                rcu_read_unlock();
        }
}

static void __execlists_hold(struct i915_request *rq)
{
        LIST_HEAD(list);

        do {
                struct i915_dependency *p;

                if (i915_request_is_active(rq))
                        __i915_request_unsubmit(rq);

                clear_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
                list_move_tail(&rq->sched.link, &rq->engine->active.hold);
                i915_request_set_hold(rq);
                RQ_TRACE(rq, "on hold\n");

                for_each_waiter(p, rq) {
                        struct i915_request *w =
                                container_of(p->waiter, typeof(*w), sched);

                        /* Leave semaphores spinning on the other engines */
                        if (w->engine != rq->engine)
                                continue;

                        if (!i915_request_is_ready(w))
                                continue;

                        if (i915_request_completed(w))
                                continue;

                        if (i915_request_on_hold(w))
                                continue;

                        list_move_tail(&w->sched.link, &list);
                }

                rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
        } while (rq);
}

static bool execlists_hold(struct intel_engine_cs *engine,
                           struct i915_request *rq)
{
        if (i915_request_on_hold(rq))
                return false;

        spin_lock_irq(&engine->active.lock);

        if (i915_request_completed(rq)) { /* too late! */
                rq = NULL;
                goto unlock;
        }

        if (rq->engine != engine) { /* preempted virtual engine */
                struct virtual_engine *ve = to_virtual_engine(rq->engine);

                /*
                 * intel_context_inflight() is only protected by virtue
                 * of process_csb() being called only by the tasklet (or
                 * directly from inside reset while the tasklet is suspended).
                 * Assert that neither of those are allowed to run while we
                 * poke at the request queues.
                 */
                GEM_BUG_ON(!reset_in_progress(&engine->execlists));

                /*
                 * An unsubmitted request along a virtual engine will
                 * remain on the active (this) engine until we are able
                 * to process the context switch away (and so mark the
                 * context as no longer in flight). That cannot have happened
                 * yet, otherwise we would not be hanging!
                 */
                spin_lock(&ve->base.active.lock);
                GEM_BUG_ON(intel_context_inflight(rq->context) != engine);
                GEM_BUG_ON(ve->request != rq);
                ve->request = NULL;
                spin_unlock(&ve->base.active.lock);
                i915_request_put(rq);

                rq->engine = engine;
        }

        /*
         * Transfer this request onto the hold queue to prevent it
         * being resumbitted to HW (and potentially completed) before we have
         * released it. Since we may have already submitted following
         * requests, we need to remove those as well.
         */
        GEM_BUG_ON(i915_request_on_hold(rq));
        GEM_BUG_ON(rq->engine != engine);
        __execlists_hold(rq);
        GEM_BUG_ON(list_empty(&engine->active.hold));

unlock:
        spin_unlock_irq(&engine->active.lock);
        return rq;
}

static bool hold_request(const struct i915_request *rq)
{
        struct i915_dependency *p;
        bool result = false;

        /*
         * If one of our ancestors is on hold, we must also be on hold,
         * otherwise we will bypass it and execute before it.
         */
        rcu_read_lock();
        for_each_signaler(p, rq) {
                const struct i915_request *s =
                        container_of(p->signaler, typeof(*s), sched);

                if (s->engine != rq->engine)
                        continue;

                result = i915_request_on_hold(s);
                if (result)
                        break;
        }
        rcu_read_unlock();

        return result;
}

static void __execlists_unhold(struct i915_request *rq)
{
        LIST_HEAD(list);

        do {
                struct i915_dependency *p;

                RQ_TRACE(rq, "hold release\n");

                GEM_BUG_ON(!i915_request_on_hold(rq));
                GEM_BUG_ON(!i915_sw_fence_signaled(&rq->submit));

                i915_request_clear_hold(rq);
                list_move_tail(&rq->sched.link,
                               i915_sched_lookup_priolist(rq->engine,
                                                          rq_prio(rq)));
                set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);

                /* Also release any children on this engine that are ready */
                for_each_waiter(p, rq) {
                        struct i915_request *w =
                                container_of(p->waiter, typeof(*w), sched);

                        /* Propagate any change in error status */
                        if (rq->fence.error)
                                i915_request_set_error_once(w, rq->fence.error);

                        if (w->engine != rq->engine)
                                continue;

                        if (!i915_request_on_hold(w))
                                continue;

                        /* Check that no other parents are also on hold */
                        if (hold_request(w))
                                continue;

                        list_move_tail(&w->sched.link, &list);
                }

                rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
        } while (rq);
}

static void execlists_unhold(struct intel_engine_cs *engine,
                             struct i915_request *rq)
{
        spin_lock_irq(&engine->active.lock);

        /*
         * Move this request back to the priority queue, and all of its
         * children and grandchildren that were suspended along with it.
         */
        __execlists_unhold(rq);

        if (rq_prio(rq) > engine->execlists.queue_priority_hint) {
                engine->execlists.queue_priority_hint = rq_prio(rq);
                tasklet_hi_schedule(&engine->execlists.tasklet);
        }

        spin_unlock_irq(&engine->active.lock);
}

struct execlists_capture {
        struct work_struct work;
        struct i915_request *rq;
        struct i915_gpu_coredump *error;
};

static void execlists_capture_work(struct work_struct *work)
{
        struct execlists_capture *cap = container_of(work, typeof(*cap), work);
        const gfp_t gfp = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN;
        struct intel_engine_cs *engine = cap->rq->engine;
        struct intel_gt_coredump *gt = cap->error->gt;
        struct intel_engine_capture_vma *vma;

        /* Compress all the objects attached to the request, slow! */
        vma = intel_engine_coredump_add_request(gt->engine, cap->rq, gfp);
        if (vma) {
                struct i915_vma_compress *compress =
                        i915_vma_capture_prepare(gt);

                intel_engine_coredump_add_vma(gt->engine, vma, compress);
                i915_vma_capture_finish(gt, compress);
        }

        gt->simulated = gt->engine->simulated;
        cap->error->simulated = gt->simulated;

        /* Publish the error state, and announce it to the world */
        i915_error_state_store(cap->error);
        i915_gpu_coredump_put(cap->error);

        /* Return this request and all that depend upon it for signaling */
        execlists_unhold(engine, cap->rq);
        i915_request_put(cap->rq);

        kfree(cap);
}

static struct execlists_capture *capture_regs(struct intel_engine_cs *engine)
{
        const gfp_t gfp = GFP_ATOMIC | __GFP_NOWARN;
        struct execlists_capture *cap;

        cap = kmalloc(sizeof(*cap), gfp);
        if (!cap)
                return NULL;

        cap->error = i915_gpu_coredump_alloc(engine->i915, gfp);
        if (!cap->error)
                goto err_cap;

        cap->error->gt = intel_gt_coredump_alloc(engine->gt, gfp);
        if (!cap->error->gt)
                goto err_gpu;

        cap->error->gt->engine = intel_engine_coredump_alloc(engine, gfp);
        if (!cap->error->gt->engine)
                goto err_gt;

        return cap;

err_gt:
        kfree(cap->error->gt);
err_gpu:
        kfree(cap->error);
err_cap:

        kfree(cap);
        return NULL;
}

static struct i915_request *
active_context(struct intel_engine_cs *engine, u32 ccid)
{
        const struct intel_engine_execlists * const el = &engine->execlists;
        struct i915_request * const *port, *rq;

        /*
         * Use the most recent result from process_csb(), but just in case
         * we trigger an error (via interrupt) before the first CS event has
         * been written, peek at the next submission.
         */

        for (port = el->active; (rq = *port); port++) {
                if (rq->context->lrc.ccid == ccid) {
                        ENGINE_TRACE(engine,
                                     "ccid found at active:%zd\n",
                                     port - el->active);
                        return rq;
                }
        }

        for (port = el->pending; (rq = *port); port++) {
                if (rq->context->lrc.ccid == ccid) {
                        ENGINE_TRACE(engine,
                                     "ccid found at pending:%zd\n",
                                     port - el->pending);
                        return rq;
                }
        }

        ENGINE_TRACE(engine, "ccid:%x not found\n", ccid);
        return NULL;
}

static u32 active_ccid(struct intel_engine_cs *engine)
{
        return ENGINE_READ_FW(engine, RING_EXECLIST_STATUS_HI);
}

static void execlists_capture(struct intel_engine_cs *engine)
{
        struct execlists_capture *cap;

        if (!IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR))
                return;

        /*
         * We need to _quickly_ capture the engine state before we reset.
         * We are inside an atomic section (softirq) here and we are delaying
         * the forced preemption event.
         */
        cap = capture_regs(engine);
        if (!cap)
                return;

        spin_lock_irq(&engine->active.lock);
        cap->rq = active_context(engine, active_ccid(engine));
        if (cap->rq) {
                cap->rq = active_request(cap->rq->context->timeline, cap->rq);
                cap->rq = i915_request_get_rcu(cap->rq);
        }
        spin_unlock_irq(&engine->active.lock);
        if (!cap->rq)
                goto err_free;

        /*
         * Remove the request from the execlists queue, and take ownership
         * of the request. We pass it to our worker who will _slowly_ compress
         * all the pages the _user_ requested for debugging their batch, after
         * which we return it to the queue for signaling.
         *
         * By removing them from the execlists queue, we also remove the
         * requests from being processed by __unwind_incomplete_requests()
         * during the intel_engine_reset(), and so they will *not* be replayed
         * afterwards.
         *
         * Note that because we have not yet reset the engine at this point,
         * it is possible for the request that we have identified as being
         * guilty, did in fact complete and we will then hit an arbitration
         * point allowing the outstanding preemption to succeed. The likelihood
         * of that is very low (as capturing of the engine registers should be
         * fast enough to run inside an irq-off atomic section!), so we will
         * simply hold that request accountable for being non-preemptible
         * long enough to force the reset.
         */
        if (!execlists_hold(engine, cap->rq))
                goto err_rq;

        INIT_WORK(&cap->work, execlists_capture_work);
        schedule_work(&cap->work);
        return;

err_rq:
        i915_request_put(cap->rq);
err_free:
        i915_gpu_coredump_put(cap->error);
        kfree(cap);
}

static void execlists_reset(struct intel_engine_cs *engine, const char *msg)
{
        const unsigned int bit = I915_RESET_ENGINE + engine->id;
        unsigned long *lock = &engine->gt->reset.flags;

        if (!intel_has_reset_engine(engine->gt))
                return;

        if (test_and_set_bit(bit, lock))
                return;

        ENGINE_TRACE(engine, "reset for %s\n", msg);

        /* Mark this tasklet as disabled to avoid waiting for it to complete */
        tasklet_disable_nosync(&engine->execlists.tasklet);

        ring_set_paused(engine, 1); /* Freeze the current request in place */
        execlists_capture(engine);
        intel_engine_reset(engine, msg);

        tasklet_enable(&engine->execlists.tasklet);
        clear_and_wake_up_bit(bit, lock);
}

static bool preempt_timeout(const struct intel_engine_cs *const engine)
{
        const struct timer_list *t = &engine->execlists.preempt;

        if (!CONFIG_DRM_I915_PREEMPT_TIMEOUT)
                return false;

        if (!timer_expired(t))
                return false;

        return READ_ONCE(engine->execlists.pending[0]);
}

/*
 * Check the unread Context Status Buffers and manage the submission of new
 * contexts to the ELSP accordingly.
 */
static void execlists_submission_tasklet(unsigned long data)
{
        struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
        bool timeout = preempt_timeout(engine);

        process_csb(engine);

        if (unlikely(READ_ONCE(engine->execlists.error_interrupt))) {
                const char *msg;

                /* Generate the error message in priority wrt to the user! */
                if (engine->execlists.error_interrupt & GENMASK(15, 0))
                        msg = "CS error"; /* thrown by a user payload */
                else if (engine->execlists.error_interrupt & ERROR_CSB)
                        msg = "invalid CSB event";
                else
                        msg = "internal error";

                engine->execlists.error_interrupt = 0;
                execlists_reset(engine, msg);
        }

        if (!READ_ONCE(engine->execlists.pending[0]) || timeout) {
                unsigned long flags;

                spin_lock_irqsave(&engine->active.lock, flags);
                __execlists_submission_tasklet(engine);
                spin_unlock_irqrestore(&engine->active.lock, flags);

                /* Recheck after serialising with direct-submission */
                if (unlikely(timeout && preempt_timeout(engine))) {
                        cancel_timer(&engine->execlists.preempt);
                        execlists_reset(engine, "preemption time out");
                }
        }
}

static void __execlists_kick(struct intel_engine_execlists *execlists)
{
        /* Kick the tasklet for some interrupt coalescing and reset handling */
        tasklet_hi_schedule(&execlists->tasklet);
}

#define execlists_kick(t, member) \
        __execlists_kick(container_of(t, struct intel_engine_execlists, member))

static void execlists_timeslice(struct timer_list *timer)
{
        execlists_kick(timer, timer);
}

static void execlists_preempt(struct timer_list *timer)
{
        execlists_kick(timer, preempt);
}

static void queue_request(struct intel_engine_cs *engine,
                          struct i915_request *rq)
{
        GEM_BUG_ON(!list_empty(&rq->sched.link));
        list_add_tail(&rq->sched.link,
                      i915_sched_lookup_priolist(engine, rq_prio(rq)));
        set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
}

static void __submit_queue_imm(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;

        if (reset_in_progress(execlists))
                return; /* defer until we restart the engine following reset */

        __execlists_submission_tasklet(engine);
}

static void submit_queue(struct intel_engine_cs *engine,
                         const struct i915_request *rq)
{
        struct intel_engine_execlists *execlists = &engine->execlists;

        if (rq_prio(rq) <= execlists->queue_priority_hint)
                return;

        execlists->queue_priority_hint = rq_prio(rq);
        __submit_queue_imm(engine);
}

static bool ancestor_on_hold(const struct intel_engine_cs *engine,
                             const struct i915_request *rq)
{
        GEM_BUG_ON(i915_request_on_hold(rq));
        return !list_empty(&engine->active.hold) && hold_request(rq);
}

static void flush_csb(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists *el = &engine->execlists;

        if (READ_ONCE(el->pending[0]) && tasklet_trylock(&el->tasklet)) {
                if (!reset_in_progress(el))
                        process_csb(engine);
                tasklet_unlock(&el->tasklet);
        }
}

static void execlists_submit_request(struct i915_request *request)
{
        struct intel_engine_cs *engine = request->engine;
        unsigned long flags;

        /* Hopefully we clear execlists->pending[] to let us through */
        flush_csb(engine);

        /* Will be called from irq-context when using foreign fences. */
        spin_lock_irqsave(&engine->active.lock, flags);

        if (unlikely(ancestor_on_hold(engine, request))) {
                RQ_TRACE(request, "ancestor on hold\n");
                list_add_tail(&request->sched.link, &engine->active.hold);
                i915_request_set_hold(request);
        } else {
                queue_request(engine, request);

                GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
                GEM_BUG_ON(list_empty(&request->sched.link));

                submit_queue(engine, request);
        }

        spin_unlock_irqrestore(&engine->active.lock, flags);
}

static void __execlists_context_fini(struct intel_context *ce)
{
        intel_ring_put(ce->ring);
        i915_vma_put(ce->state);
}

static void execlists_context_destroy(struct kref *kref)
{
        struct intel_context *ce = container_of(kref, typeof(*ce), ref);

        GEM_BUG_ON(!i915_active_is_idle(&ce->active));
        GEM_BUG_ON(intel_context_is_pinned(ce));

        if (ce->state)
                __execlists_context_fini(ce);

        intel_context_fini(ce);
        intel_context_free(ce);
}

static void
set_redzone(void *vaddr, const struct intel_engine_cs *engine)
{
        if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
                return;

        vaddr += engine->context_size;

        memset(vaddr, CONTEXT_REDZONE, I915_GTT_PAGE_SIZE);
}

static void
check_redzone(const void *vaddr, const struct intel_engine_cs *engine)
{
        if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
                return;

        vaddr += engine->context_size;

        if (memchr_inv(vaddr, CONTEXT_REDZONE, I915_GTT_PAGE_SIZE))
                drm_err_once(&engine->i915->drm,
                             "%s context redzone overwritten!\n",
                             engine->name);
}

static void execlists_context_unpin(struct intel_context *ce)
{
        check_redzone((void *)ce->lrc_reg_state - LRC_STATE_OFFSET,
                      ce->engine);
}

static void execlists_context_post_unpin(struct intel_context *ce)
{
        i915_gem_object_unpin_map(ce->state->obj);
}

static u32 *
gen12_emit_timestamp_wa(const struct intel_context *ce, u32 *cs)
{
        *cs++ = MI_LOAD_REGISTER_MEM_GEN8 |
                MI_SRM_LRM_GLOBAL_GTT |
                MI_LRI_LRM_CS_MMIO;
        *cs++ = i915_mmio_reg_offset(GEN8_RING_CS_GPR(0, 0));
        *cs++ = i915_ggtt_offset(ce->state) + LRC_STATE_OFFSET +
                CTX_TIMESTAMP * sizeof(u32);
        *cs++ = 0;

        *cs++ = MI_LOAD_REGISTER_REG |
                MI_LRR_SOURCE_CS_MMIO |
                MI_LRI_LRM_CS_MMIO;
        *cs++ = i915_mmio_reg_offset(GEN8_RING_CS_GPR(0, 0));
        *cs++ = i915_mmio_reg_offset(RING_CTX_TIMESTAMP(0));

        *cs++ = MI_LOAD_REGISTER_REG |
                MI_LRR_SOURCE_CS_MMIO |
                MI_LRI_LRM_CS_MMIO;
        *cs++ = i915_mmio_reg_offset(GEN8_RING_CS_GPR(0, 0));
        *cs++ = i915_mmio_reg_offset(RING_CTX_TIMESTAMP(0));

        return cs;
}

static u32 *
gen12_emit_restore_scratch(const struct intel_context *ce, u32 *cs)
{
        GEM_BUG_ON(lrc_ring_gpr0(ce->engine) == -1);

        *cs++ = MI_LOAD_REGISTER_MEM_GEN8 |
                MI_SRM_LRM_GLOBAL_GTT |
                MI_LRI_LRM_CS_MMIO;
        *cs++ = i915_mmio_reg_offset(GEN8_RING_CS_GPR(0, 0));
        *cs++ = i915_ggtt_offset(ce->state) + LRC_STATE_OFFSET +
                (lrc_ring_gpr0(ce->engine) + 1) * sizeof(u32);
        *cs++ = 0;

        return cs;
}

static u32 *
gen12_emit_cmd_buf_wa(const struct intel_context *ce, u32 *cs)
{
        GEM_BUG_ON(lrc_ring_cmd_buf_cctl(ce->engine) == -1);

        *cs++ = MI_LOAD_REGISTER_MEM_GEN8 |
                MI_SRM_LRM_GLOBAL_GTT |
                MI_LRI_LRM_CS_MMIO;
        *cs++ = i915_mmio_reg_offset(GEN8_RING_CS_GPR(0, 0));
        *cs++ = i915_ggtt_offset(ce->state) + LRC_STATE_OFFSET +
                (lrc_ring_cmd_buf_cctl(ce->engine) + 1) * sizeof(u32);
        *cs++ = 0;

        *cs++ = MI_LOAD_REGISTER_REG |
                MI_LRR_SOURCE_CS_MMIO |
                MI_LRI_LRM_CS_MMIO;
        *cs++ = i915_mmio_reg_offset(GEN8_RING_CS_GPR(0, 0));
        *cs++ = i915_mmio_reg_offset(RING_CMD_BUF_CCTL(0));

        return cs;
}

static u32 *
gen12_emit_indirect_ctx_rcs(const struct intel_context *ce, u32 *cs)
{
        cs = gen12_emit_timestamp_wa(ce, cs);
        cs = gen12_emit_cmd_buf_wa(ce, cs);
        cs = gen12_emit_restore_scratch(ce, cs);

        return cs;
}

static u32 *
gen12_emit_indirect_ctx_xcs(const struct intel_context *ce, u32 *cs)
{
        cs = gen12_emit_timestamp_wa(ce, cs);
        cs = gen12_emit_restore_scratch(ce, cs);

        return cs;
}

static inline u32 context_wa_bb_offset(const struct intel_context *ce)
{
        return PAGE_SIZE * ce->wa_bb_page;
}

static u32 *context_indirect_bb(const struct intel_context *ce)
{
        void *ptr;

        GEM_BUG_ON(!ce->wa_bb_page);

        ptr = ce->lrc_reg_state;
        ptr -= LRC_STATE_OFFSET; /* back to start of context image */
        ptr += context_wa_bb_offset(ce);

        return ptr;
}

static void
setup_indirect_ctx_bb(const struct intel_context *ce,
                      const struct intel_engine_cs *engine,
                      u32 *(*emit)(const struct intel_context *, u32 *))
{
        u32 * const start = context_indirect_bb(ce);
        u32 *cs;

        cs = emit(ce, start);
        GEM_BUG_ON(cs - start > I915_GTT_PAGE_SIZE / sizeof(*cs));
        while ((unsigned long)cs % CACHELINE_BYTES)
                *cs++ = MI_NOOP;

        lrc_ring_setup_indirect_ctx(ce->lrc_reg_state, engine,
                                    i915_ggtt_offset(ce->state) +
                                    context_wa_bb_offset(ce),
                                    (cs - start) * sizeof(*cs));
}

static void
__execlists_update_reg_state(const struct intel_context *ce,
                             const struct intel_engine_cs *engine,
                             u32 head)
{
        struct intel_ring *ring = ce->ring;
        u32 *regs = ce->lrc_reg_state;

        GEM_BUG_ON(!intel_ring_offset_valid(ring, head));
        GEM_BUG_ON(!intel_ring_offset_valid(ring, ring->tail));

        regs[CTX_RING_START] = i915_ggtt_offset(ring->vma);
        regs[CTX_RING_HEAD] = head;
        regs[CTX_RING_TAIL] = ring->tail;
        regs[CTX_RING_CTL] = RING_CTL_SIZE(ring->size) | RING_VALID;

        /* RPCS */
        if (engine->class == RENDER_CLASS) {
                regs[CTX_R_PWR_CLK_STATE] =
                        intel_sseu_make_rpcs(engine->gt, &ce->sseu);

                i915_oa_init_reg_state(ce, engine);
        }

        if (ce->wa_bb_page) {
                u32 *(*fn)(const struct intel_context *ce, u32 *cs);

                fn = gen12_emit_indirect_ctx_xcs;
                if (ce->engine->class == RENDER_CLASS)
                        fn = gen12_emit_indirect_ctx_rcs;

                /* Mutually exclusive wrt to global indirect bb */
                GEM_BUG_ON(engine->wa_ctx.indirect_ctx.size);
                setup_indirect_ctx_bb(ce, engine, fn);
        }
}

static int
execlists_context_pre_pin(struct intel_context *ce,
                          struct i915_gem_ww_ctx *ww, void **vaddr)
{
        GEM_BUG_ON(!ce->state);
        GEM_BUG_ON(!i915_vma_is_pinned(ce->state));

        *vaddr = i915_gem_object_pin_map(ce->state->obj,
                                        i915_coherent_map_type(ce->engine->i915) |
                                        I915_MAP_OVERRIDE);

        return PTR_ERR_OR_ZERO(*vaddr);
}

static int
__execlists_context_pin(struct intel_context *ce,
                        struct intel_engine_cs *engine,
                        void *vaddr)
{
        ce->lrc.lrca = lrc_descriptor(ce, engine) | CTX_DESC_FORCE_RESTORE;
        ce->lrc_reg_state = vaddr + LRC_STATE_OFFSET;
        __execlists_update_reg_state(ce, engine, ce->ring->tail);

        return 0;
}

static int execlists_context_pin(struct intel_context *ce, void *vaddr)
{
        return __execlists_context_pin(ce, ce->engine, vaddr);
}

static int execlists_context_alloc(struct intel_context *ce)
{
        return __execlists_context_alloc(ce, ce->engine);
}

static void execlists_context_reset(struct intel_context *ce)
{
        CE_TRACE(ce, "reset\n");
        GEM_BUG_ON(!intel_context_is_pinned(ce));

        intel_ring_reset(ce->ring, ce->ring->emit);

        /* Scrub away the garbage */
        execlists_init_reg_state(ce->lrc_reg_state,
                                 ce, ce->engine, ce->ring, true);
        __execlists_update_reg_state(ce, ce->engine, ce->ring->tail);

        ce->lrc.desc |= CTX_DESC_FORCE_RESTORE;
}

static const struct intel_context_ops execlists_context_ops = {
        .alloc = execlists_context_alloc,

        .pre_pin = execlists_context_pre_pin,
        .pin = execlists_context_pin,
        .unpin = execlists_context_unpin,
        .post_unpin = execlists_context_post_unpin,

        .enter = intel_context_enter_engine,
        .exit = intel_context_exit_engine,

        .reset = execlists_context_reset,
        .destroy = execlists_context_destroy,
};

static u32 hwsp_offset(const struct i915_request *rq)
{
        const struct intel_timeline_cacheline *cl;

        /* Before the request is executed, the timeline/cachline is fixed */

        cl = rcu_dereference_protected(rq->hwsp_cacheline, 1);
        if (cl)
                return cl->ggtt_offset;

        return rcu_dereference_protected(rq->timeline, 1)->hwsp_offset;
}

static int gen8_emit_init_breadcrumb(struct i915_request *rq)
{
        u32 *cs;

        GEM_BUG_ON(i915_request_has_initial_breadcrumb(rq));
        if (!i915_request_timeline(rq)->has_initial_breadcrumb)
                return 0;

        cs = intel_ring_begin(rq, 6);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        /*
         * Check if we have been preempted before we even get started.
         *
         * After this point i915_request_started() reports true, even if
         * we get preempted and so are no longer running.
         */
        *cs++ = MI_ARB_CHECK;
        *cs++ = MI_NOOP;

        *cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
        *cs++ = hwsp_offset(rq);
        *cs++ = 0;
        *cs++ = rq->fence.seqno - 1;

        intel_ring_advance(rq, cs);

        /* Record the updated position of the request's payload */
        rq->infix = intel_ring_offset(rq, cs);

        __set_bit(I915_FENCE_FLAG_INITIAL_BREADCRUMB, &rq->fence.flags);

        return 0;
}

static int emit_pdps(struct i915_request *rq)
{
        const struct intel_engine_cs * const engine = rq->engine;
        struct i915_ppgtt * const ppgtt = i915_vm_to_ppgtt(rq->context->vm);
        int err, i;
        u32 *cs;

        GEM_BUG_ON(intel_vgpu_active(rq->engine->i915));

        /*
         * Beware ye of the dragons, this sequence is magic!
         *
         * Small changes to this sequence can cause anything from
         * GPU hangs to forcewake errors and machine lockups!
         */

        /* Flush any residual operations from the context load */
        err = engine->emit_flush(rq, EMIT_FLUSH);
        if (err)
                return err;

        /* Magic required to prevent forcewake errors! */
        err = engine->emit_flush(rq, EMIT_INVALIDATE);
        if (err)
                return err;

        cs = intel_ring_begin(rq, 4 * GEN8_3LVL_PDPES + 2);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        /* Ensure the LRI have landed before we invalidate & continue */
        *cs++ = MI_LOAD_REGISTER_IMM(2 * GEN8_3LVL_PDPES) | MI_LRI_FORCE_POSTED;
        for (i = GEN8_3LVL_PDPES; i--; ) {
                const dma_addr_t pd_daddr = i915_page_dir_dma_addr(ppgtt, i);
                u32 base = engine->mmio_base;

                *cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, i));
                *cs++ = upper_32_bits(pd_daddr);
                *cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(base, i));
                *cs++ = lower_32_bits(pd_daddr);
        }
        *cs++ = MI_NOOP;

        intel_ring_advance(rq, cs);

        return 0;
}

static int execlists_request_alloc(struct i915_request *request)
{
        int ret;

        GEM_BUG_ON(!intel_context_is_pinned(request->context));

        /*
         * Flush enough space to reduce the likelihood of waiting after
         * we start building the request - in which case we will just
         * have to repeat work.
         */
        request->reserved_space += EXECLISTS_REQUEST_SIZE;

        /*
         * Note that after this point, we have committed to using
         * this request as it is being used to both track the
         * state of engine initialisation and liveness of the
         * golden renderstate above. Think twice before you try
         * to cancel/unwind this request now.
         */

        if (!i915_vm_is_4lvl(request->context->vm)) {
                ret = emit_pdps(request);
                if (ret)
                        return ret;
        }

        /* Unconditionally invalidate GPU caches and TLBs. */
        ret = request->engine->emit_flush(request, EMIT_INVALIDATE);
        if (ret)
                return ret;

        request->reserved_space -= EXECLISTS_REQUEST_SIZE;
        return 0;
}

/*
 * In this WA we need to set GEN8_L3SQCREG4[21:21] and reset it after
 * PIPE_CONTROL instruction. This is required for the flush to happen correctly
 * but there is a slight complication as this is applied in WA batch where the
 * values are only initialized once so we cannot take register value at the
 * beginning and reuse it further; hence we save its value to memory, upload a
 * constant value with bit21 set and then we restore it back with the saved value.
 * To simplify the WA, a constant value is formed by using the default value
 * of this register. This shouldn't be a problem because we are only modifying
 * it for a short period and this batch in non-premptible. We can ofcourse
 * use additional instructions that read the actual value of the register
 * at that time and set our bit of interest but it makes the WA complicated.
 *
 * This WA is also required for Gen9 so extracting as a function avoids
 * code duplication.
 */
static u32 *
gen8_emit_flush_coherentl3_wa(struct intel_engine_cs *engine, u32 *batch)
{
        /* NB no one else is allowed to scribble over scratch + 256! */
        *batch++ = MI_STORE_REGISTER_MEM_GEN8 | MI_SRM_LRM_GLOBAL_GTT;
        *batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
        *batch++ = intel_gt_scratch_offset(engine->gt,
                                           INTEL_GT_SCRATCH_FIELD_COHERENTL3_WA);
        *batch++ = 0;

        *batch++ = MI_LOAD_REGISTER_IMM(1);
        *batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
        *batch++ = 0x40400000 | GEN8_LQSC_FLUSH_COHERENT_LINES;

        batch = gen8_emit_pipe_control(batch,
                                       PIPE_CONTROL_CS_STALL |
                                       PIPE_CONTROL_DC_FLUSH_ENABLE,
                                       0);

        *batch++ = MI_LOAD_REGISTER_MEM_GEN8 | MI_SRM_LRM_GLOBAL_GTT;
        *batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
        *batch++ = intel_gt_scratch_offset(engine->gt,
                                           INTEL_GT_SCRATCH_FIELD_COHERENTL3_WA);
        *batch++ = 0;

        return batch;
}

/*
 * Typically we only have one indirect_ctx and per_ctx batch buffer which are
 * initialized at the beginning and shared across all contexts but this field
 * helps us to have multiple batches at different offsets and select them based
 * on a criteria. At the moment this batch always start at the beginning of the page
 * and at this point we don't have multiple wa_ctx batch buffers.
 *
 * The number of WA applied are not known at the beginning; we use this field
 * to return the no of DWORDS written.
 *
 * It is to be noted that this batch does not contain MI_BATCH_BUFFER_END
 * so it adds NOOPs as padding to make it cacheline aligned.
 * MI_BATCH_BUFFER_END will be added to perctx batch and both of them together
 * makes a complete batch buffer.
 */
static u32 *gen8_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
{
        /* WaDisableCtxRestoreArbitration:bdw,chv */
        *batch++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;

        /* WaFlushCoherentL3CacheLinesAtContextSwitch:bdw */
        if (IS_BROADWELL(engine->i915))
                batch = gen8_emit_flush_coherentl3_wa(engine, batch);

        /* WaClearSlmSpaceAtContextSwitch:bdw,chv */
        /* Actual scratch location is at 128 bytes offset */
        batch = gen8_emit_pipe_control(batch,
                                       PIPE_CONTROL_FLUSH_L3 |
                                       PIPE_CONTROL_STORE_DATA_INDEX |
                                       PIPE_CONTROL_CS_STALL |
                                       PIPE_CONTROL_QW_WRITE,
                                       LRC_PPHWSP_SCRATCH_ADDR);

        *batch++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;

        /* Pad to end of cacheline */
        while ((unsigned long)batch % CACHELINE_BYTES)
                *batch++ = MI_NOOP;

        /*
         * MI_BATCH_BUFFER_END is not required in Indirect ctx BB because
         * execution depends on the length specified in terms of cache lines
         * in the register CTX_RCS_INDIRECT_CTX
         */

        return batch;
}

struct lri {
        i915_reg_t reg;
        u32 value;
};

static u32 *emit_lri(u32 *batch, const struct lri *lri, unsigned int count)
{
        GEM_BUG_ON(!count || count > 63);

        *batch++ = MI_LOAD_REGISTER_IMM(count);
        do {
                *batch++ = i915_mmio_reg_offset(lri->reg);
                *batch++ = lri->value;
        } while (lri++, --count);
        *batch++ = MI_NOOP;

        return batch;
}

static u32 *gen9_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
{
        static const struct lri lri[] = {
                /* WaDisableGatherAtSetShaderCommonSlice:skl,bxt,kbl,glk */
                {
                        COMMON_SLICE_CHICKEN2,
                        __MASKED_FIELD(GEN9_DISABLE_GATHER_AT_SET_SHADER_COMMON_SLICE,
                                       0),
                },

                /* BSpec: 11391 */
                {
                        FF_SLICE_CHICKEN,
                        __MASKED_FIELD(FF_SLICE_CHICKEN_CL_PROVOKING_VERTEX_FIX,
                                       FF_SLICE_CHICKEN_CL_PROVOKING_VERTEX_FIX),
                },

                /* BSpec: 11299 */
                {
                        _3D_CHICKEN3,
                        __MASKED_FIELD(_3D_CHICKEN_SF_PROVOKING_VERTEX_FIX,
                                       _3D_CHICKEN_SF_PROVOKING_VERTEX_FIX),
                }
        };

        *batch++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;

        /* WaFlushCoherentL3CacheLinesAtContextSwitch:skl,bxt,glk */
        batch = gen8_emit_flush_coherentl3_wa(engine, batch);

        /* WaClearSlmSpaceAtContextSwitch:skl,bxt,kbl,glk,cfl */
        batch = gen8_emit_pipe_control(batch,
                                       PIPE_CONTROL_FLUSH_L3 |
                                       PIPE_CONTROL_STORE_DATA_INDEX |
                                       PIPE_CONTROL_CS_STALL |
                                       PIPE_CONTROL_QW_WRITE,
                                       LRC_PPHWSP_SCRATCH_ADDR);

        batch = emit_lri(batch, lri, ARRAY_SIZE(lri));

        /* WaMediaPoolStateCmdInWABB:bxt,glk */
        if (HAS_POOLED_EU(engine->i915)) {
                /*
                 * EU pool configuration is setup along with golden context
                 * during context initialization. This value depends on
                 * device type (2x6 or 3x6) and needs to be updated based
                 * on which subslice is disabled especially for 2x6
                 * devices, however it is safe to load default
                 * configuration of 3x6 device instead of masking off
                 * corresponding bits because HW ignores bits of a disabled
                 * subslice and drops down to appropriate config. Please
                 * see render_state_setup() in i915_gem_render_state.c for
                 * possible configurations, to avoid duplication they are
                 * not shown here again.
                 */
                *batch++ = GEN9_MEDIA_POOL_STATE;
                *batch++ = GEN9_MEDIA_POOL_ENABLE;
                *batch++ = 0x00777000;
                *batch++ = 0;
                *batch++ = 0;
                *batch++ = 0;
        }

        *batch++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;

        /* Pad to end of cacheline */
        while ((unsigned long)batch % CACHELINE_BYTES)
                *batch++ = MI_NOOP;

        return batch;
}

static u32 *
gen10_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
{
        int i;

        /*
         * WaPipeControlBefore3DStateSamplePattern: cnl
         *
         * Ensure the engine is idle prior to programming a
         * 3DSTATE_SAMPLE_PATTERN during a context restore.
         */
        batch = gen8_emit_pipe_control(batch,
                                       PIPE_CONTROL_CS_STALL,
                                       0);
        /*
         * WaPipeControlBefore3DStateSamplePattern says we need 4 dwords for
         * the PIPE_CONTROL followed by 12 dwords of 0x0, so 16 dwords in
         * total. However, a PIPE_CONTROL is 6 dwords long, not 4, which is
         * confusing. Since gen8_emit_pipe_control() already advances the
         * batch by 6 dwords, we advance the other 10 here, completing a
         * cacheline. It's not clear if the workaround requires this padding
         * before other commands, or if it's just the regular padding we would
         * already have for the workaround bb, so leave it here for now.
         */
        for (i = 0; i < 10; i++)
                *batch++ = MI_NOOP;

        /* Pad to end of cacheline */
        while ((unsigned long)batch % CACHELINE_BYTES)
                *batch++ = MI_NOOP;

        return batch;
}

#define CTX_WA_BB_OBJ_SIZE (PAGE_SIZE)

static int lrc_setup_wa_ctx(struct intel_engine_cs *engine)
{
        struct drm_i915_gem_object *obj;
        struct i915_vma *vma;
        int err;

        obj = i915_gem_object_create_shmem(engine->i915, CTX_WA_BB_OBJ_SIZE);
        if (IS_ERR(obj))
                return PTR_ERR(obj);

        vma = i915_vma_instance(obj, &engine->gt->ggtt->vm, NULL);
        if (IS_ERR(vma)) {
                err = PTR_ERR(vma);
                goto err;
        }

        err = i915_ggtt_pin(vma, NULL, 0, PIN_HIGH);
        if (err)
                goto err;

        engine->wa_ctx.vma = vma;
        return 0;

err:
        i915_gem_object_put(obj);
        return err;
}

static void lrc_destroy_wa_ctx(struct intel_engine_cs *engine)
{
        i915_vma_unpin_and_release(&engine->wa_ctx.vma, 0);
}

typedef u32 *(*wa_bb_func_t)(struct intel_engine_cs *engine, u32 *batch);

static int intel_init_workaround_bb(struct intel_engine_cs *engine)
{
        struct i915_ctx_workarounds *wa_ctx = &engine->wa_ctx;
        struct i915_wa_ctx_bb *wa_bb[2] = { &wa_ctx->indirect_ctx,
                                            &wa_ctx->per_ctx };
        wa_bb_func_t wa_bb_fn[2];
        void *batch, *batch_ptr;
        unsigned int i;
        int ret;

        if (engine->class != RENDER_CLASS)
                return 0;

        switch (INTEL_GEN(engine->i915)) {
        case 12:
        case 11:
                return 0;
        case 10:
                wa_bb_fn[0] = gen10_init_indirectctx_bb;
                wa_bb_fn[1] = NULL;
                break;
        case 9:
                wa_bb_fn[0] = gen9_init_indirectctx_bb;
                wa_bb_fn[1] = NULL;
                break;
        case 8:
                wa_bb_fn[0] = gen8_init_indirectctx_bb;
                wa_bb_fn[1] = NULL;
                break;
        default:
                MISSING_CASE(INTEL_GEN(engine->i915));
                return 0;
        }

        ret = lrc_setup_wa_ctx(engine);
        if (ret) {
                drm_dbg(&engine->i915->drm,
                        "Failed to setup context WA page: %d\n", ret);
                return ret;
        }

        batch = i915_gem_object_pin_map(wa_ctx->vma->obj, I915_MAP_WB);

        /*
         * Emit the two workaround batch buffers, recording the offset from the
         * start of the workaround batch buffer object for each and their
         * respective sizes.
         */
        batch_ptr = batch;
        for (i = 0; i < ARRAY_SIZE(wa_bb_fn); i++) {
                wa_bb[i]->offset = batch_ptr - batch;
                if (GEM_DEBUG_WARN_ON(!IS_ALIGNED(wa_bb[i]->offset,
                                                  CACHELINE_BYTES))) {
                        ret = -EINVAL;
                        break;
                }
                if (wa_bb_fn[i])
                        batch_ptr = wa_bb_fn[i](engine, batch_ptr);