/*
 * Xen event channels (2-level ABI)
 *
 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/linkage.h>
#include <linux/interrupt.h>
#include <linux/irq.h>

#include <asm/sync_bitops.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>

#include <xen/xen.h>
#include <xen/xen-ops.h>
#include <xen/events.h>
#include <xen/interface/xen.h>
#include <xen/interface/event_channel.h>

#include "events_internal.h"

/*
 * Note sizeof(xen_ulong_t) can be more than sizeof(unsigned long). Be
 * careful to only use bitops which allow for this (e.g
 * test_bit/find_first_bit and friends but not __ffs) and to pass
 * BITS_PER_EVTCHN_WORD as the bitmask length.
 */
#define BITS_PER_EVTCHN_WORD (sizeof(xen_ulong_t)*8)
/*
 * Make a bitmask (i.e. unsigned long *) of a xen_ulong_t
 * array. Primarily to avoid long lines (hence the terse name).
 */
#define BM(x) (unsigned long *)(x)
/* Find the first set bit in a evtchn mask */
#define EVTCHN_FIRST_BIT(w) find_first_bit(BM(&(w)), BITS_PER_EVTCHN_WORD)

#define EVTCHN_MASK_SIZE (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)

static DEFINE_PER_CPU(xen_ulong_t [EVTCHN_MASK_SIZE], cpu_evtchn_mask);

static unsigned evtchn_2l_max_channels(void)
{
        return EVTCHN_2L_NR_CHANNELS;
}

static void evtchn_2l_bind_to_cpu(struct irq_info *info, unsigned cpu)
{
        clear_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, info->cpu)));
        set_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
}

static void evtchn_2l_clear_pending(unsigned port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        sync_clear_bit(port, BM(&s->evtchn_pending[0]));
}

static void evtchn_2l_set_pending(unsigned port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        sync_set_bit(port, BM(&s->evtchn_pending[0]));
}

static bool evtchn_2l_is_pending(unsigned port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        return sync_test_bit(port, BM(&s->evtchn_pending[0]));
}

static bool evtchn_2l_test_and_set_mask(unsigned port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        return sync_test_and_set_bit(port, BM(&s->evtchn_mask[0]));
}

static void evtchn_2l_mask(unsigned port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        sync_set_bit(port, BM(&s->evtchn_mask[0]));
}

static void evtchn_2l_unmask(unsigned port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        unsigned int cpu = get_cpu();
        int do_hypercall = 0, evtchn_pending = 0;

        BUG_ON(!irqs_disabled());

        if (unlikely((cpu != cpu_from_evtchn(port))))
                do_hypercall = 1;
        else {
                /*
                 * Need to clear the mask before checking pending to
                 * avoid a race with an event becoming pending.
                 *
                 * EVTCHNOP_unmask will only trigger an upcall if the
                 * mask bit was set, so if a hypercall is needed
                 * remask the event.
                 */
                sync_clear_bit(port, BM(&s->evtchn_mask[0]));
                evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));

                if (unlikely(evtchn_pending && xen_hvm_domain())) {
                        sync_set_bit(port, BM(&s->evtchn_mask[0]));
                        do_hypercall = 1;
                }
        }

        /* Slow path (hypercall) if this is a non-local port or if this is
         * an hvm domain and an event is pending (hvm domains don't have
         * their own implementation of irq_enable). */
        if (do_hypercall) {
                struct evtchn_unmask unmask = { .port = port };
                (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
        } else {
                struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);

                /*
                 * The following is basically the equivalent of
                 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
                 * the interrupt edge' if the channel is masked.
                 */
                if (evtchn_pending &&
                    !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
                                           BM(&vcpu_info->evtchn_pending_sel)))
                        vcpu_info->evtchn_upcall_pending = 1;
        }

        put_cpu();
}

static DEFINE_PER_CPU(unsigned int, current_word_idx);
static DEFINE_PER_CPU(unsigned int, current_bit_idx);

/*
 * Mask out the i least significant bits of w
 */
#define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))

static inline xen_ulong_t active_evtchns(unsigned int cpu,
                                         struct shared_info *sh,
                                         unsigned int idx)
{
        return sh->evtchn_pending[idx] &
                per_cpu(cpu_evtchn_mask, cpu)[idx] &
                ~sh->evtchn_mask[idx];
}

/*
 * Search the CPU's pending events bitmasks.  For each one found, map
 * the event number to an irq, and feed it into do_IRQ() for handling.
 *
 * Xen uses a two-level bitmap to speed searching.  The first level is
 * a bitset of words which contain pending event bits.  The second
 * level is a bitset of pending events themselves.
 */
static void evtchn_2l_handle_events(unsigned cpu)
{
        int irq;
        xen_ulong_t pending_words;
        xen_ulong_t pending_bits;
        int start_word_idx, start_bit_idx;
        int word_idx, bit_idx;
        int i;
        struct shared_info *s = HYPERVISOR_shared_info;
        struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);

        /* Timer interrupt has highest priority. */
        irq = irq_from_virq(cpu, VIRQ_TIMER);
        if (irq != -1) {
                unsigned int evtchn = evtchn_from_irq(irq);
                word_idx = evtchn / BITS_PER_LONG;
                bit_idx = evtchn % BITS_PER_LONG;
                if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
                        generic_handle_irq(irq);
        }

        /*
         * Master flag must be cleared /before/ clearing
         * selector flag. xchg_xen_ulong must contain an
         * appropriate barrier.
         */
        pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);

        start_word_idx = __this_cpu_read(current_word_idx);
        start_bit_idx = __this_cpu_read(current_bit_idx);

        word_idx = start_word_idx;

        for (i = 0; pending_words != 0; i++) {
                xen_ulong_t words;

                words = MASK_LSBS(pending_words, word_idx);

                /*
                 * If we masked out all events, wrap to beginning.
                 */
                if (words == 0) {
                        word_idx = 0;
                        bit_idx = 0;
                        continue;
                }
                word_idx = EVTCHN_FIRST_BIT(words);

                pending_bits = active_evtchns(cpu, s, word_idx);
                bit_idx = 0; /* usually scan entire word from start */
                /*
                 * We scan the starting word in two parts.
                 *
                 * 1st time: start in the middle, scanning the
                 * upper bits.
                 *
                 * 2nd time: scan the whole word (not just the
                 * parts skipped in the first pass) -- if an
                 * event in the previously scanned bits is
                 * pending again it would just be scanned on
                 * the next loop anyway.
                 */
                if (word_idx == start_word_idx) {
                        if (i == 0)
                                bit_idx = start_bit_idx;
                }

                do {
                        xen_ulong_t bits;
                        int port;

                        bits = MASK_LSBS(pending_bits, bit_idx);

                        /* If we masked out all events, move on. */
                        if (bits == 0)
                                break;

                        bit_idx = EVTCHN_FIRST_BIT(bits);

                        /* Process port. */
                        port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
                        irq = get_evtchn_to_irq(port);

                        if (irq != -1)
                                generic_handle_irq(irq);

                        bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;

                        /* Next caller starts at last processed + 1 */
                        __this_cpu_write(current_word_idx,
                                         bit_idx ? word_idx :
                                         (word_idx+1) % BITS_PER_EVTCHN_WORD);
                        __this_cpu_write(current_bit_idx, bit_idx);
                } while (bit_idx != 0);

                /* Scan start_l1i twice; all others once. */
                if ((word_idx != start_word_idx) || (i != 0))
                        pending_words &= ~(1UL << word_idx);

                word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
        }
}

irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
{
        struct shared_info *sh = HYPERVISOR_shared_info;
        int cpu = smp_processor_id();
        xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
        int i;
        unsigned long flags;
        static DEFINE_SPINLOCK(debug_lock);
        struct vcpu_info *v;

        spin_lock_irqsave(&debug_lock, flags);

        printk("\nvcpu %d\n  ", cpu);

        for_each_online_cpu(i) {
                int pending;
                v = per_cpu(xen_vcpu, i);
                pending = (get_irq_regs() && i == cpu)
                        ? xen_irqs_disabled(get_irq_regs())
                        : v->evtchn_upcall_mask;
                printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n  ", i,
                       pending, v->evtchn_upcall_pending,
                       (int)(sizeof(v->evtchn_pending_sel)*2),
                       v->evtchn_pending_sel);
        }
        v = per_cpu(xen_vcpu, cpu);

        printk("\npending:\n   ");
        for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
                printk("%0*"PRI_xen_ulong"%s",
                       (int)sizeof(sh->evtchn_pending[0])*2,
                       sh->evtchn_pending[i],
                       i % 8 == 0 ? "\n   " : " ");
        printk("\nglobal mask:\n   ");
        for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
                printk("%0*"PRI_xen_ulong"%s",
                       (int)(sizeof(sh->evtchn_mask[0])*2),
                       sh->evtchn_mask[i],
                       i % 8 == 0 ? "\n   " : " ");

        printk("\nglobally unmasked:\n   ");
        for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
                printk("%0*"PRI_xen_ulong"%s",
                       (int)(sizeof(sh->evtchn_mask[0])*2),
                       sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
                       i % 8 == 0 ? "\n   " : " ");

        printk("\nlocal cpu%d mask:\n   ", cpu);
        for (i = (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
                printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
                       cpu_evtchn[i],
                       i % 8 == 0 ? "\n   " : " ");

        printk("\nlocally unmasked:\n   ");
        for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
                xen_ulong_t pending = sh->evtchn_pending[i]
                        & ~sh->evtchn_mask[i]
                        & cpu_evtchn[i];
                printk("%0*"PRI_xen_ulong"%s",
                       (int)(sizeof(sh->evtchn_mask[0])*2),
                       pending, i % 8 == 0 ? "\n   " : " ");
        }

        printk("\npending list:\n");
        for (i = 0; i < EVTCHN_2L_NR_CHANNELS; i++) {
                if (sync_test_bit(i, BM(sh->evtchn_pending))) {
                        int word_idx = i / BITS_PER_EVTCHN_WORD;
                        printk("  %d: event %d -> irq %d%s%s%s\n",
                               cpu_from_evtchn(i), i,
                               get_evtchn_to_irq(i),
                               sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
                               ? "" : " l2-clear",
                               !sync_test_bit(i, BM(sh->evtchn_mask))
                               ? "" : " globally-masked",
                               sync_test_bit(i, BM(cpu_evtchn))
                               ? "" : " locally-masked");
                }
        }

        spin_unlock_irqrestore(&debug_lock, flags);

        return IRQ_HANDLED;
}

static void evtchn_2l_resume(void)
{
        int i;

        for_each_online_cpu(i)
                memset(per_cpu(cpu_evtchn_mask, i), 0, sizeof(xen_ulong_t) *
                                EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
}

static const struct evtchn_ops evtchn_ops_2l = {
        .max_channels      = evtchn_2l_max_channels,
        .nr_channels       = evtchn_2l_max_channels,
        .bind_to_cpu       = evtchn_2l_bind_to_cpu,
        .clear_pending     = evtchn_2l_clear_pending,
        .set_pending       = evtchn_2l_set_pending,
        .is_pending        = evtchn_2l_is_pending,
        .test_and_set_mask = evtchn_2l_test_and_set_mask,
        .mask              = evtchn_2l_mask,
        .unmask            = evtchn_2l_unmask,
        .handle_events     = evtchn_2l_handle_events,
        .resume            = evtchn_2l_resume,
};

void __init xen_evtchn_2l_init(void)
{
        pr_info("Using 2-level ABI\n");
        evtchn_ops = &evtchn_ops_2l;
}