/*
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 *
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/hyperv.h>
#include <linux/version.h>
#include <linux/random.h>
#include <linux/clockchips.h>
#include <asm/mshyperv.h>
#include "hyperv_vmbus.h"

/* The one and only */
struct hv_context hv_context;

/*
 * If false, we're using the old mechanism for stimer0 interrupts
 * where it sends a VMbus message when it expires. The old
 * mechanism is used when running on older versions of Hyper-V
 * that don't support Direct Mode. While Hyper-V provides
 * four stimer's per CPU, Linux uses only stimer0.
 */
static bool direct_mode_enabled;
static int stimer0_irq;
static int stimer0_vector;

#define HV_TIMER_FREQUENCY (10 * 1000 * 1000) /* 100ns period */
#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
#define HV_MIN_DELTA_TICKS 1

/*
 * hv_init - Main initialization routine.
 *
 * This routine must be called before any other routines in here are called
 */
int hv_init(void)
{
        hv_context.cpu_context = alloc_percpu(struct hv_per_cpu_context);
        if (!hv_context.cpu_context)
                return -ENOMEM;

        direct_mode_enabled = ms_hyperv.misc_features &
                        HV_STIMER_DIRECT_MODE_AVAILABLE;
        return 0;
}

/*
 * hv_post_message - Post a message using the hypervisor message IPC.
 *
 * This involves a hypercall.
 */
int hv_post_message(union hv_connection_id connection_id,
                  enum hv_message_type message_type,
                  void *payload, size_t payload_size)
{
        struct hv_input_post_message *aligned_msg;
        struct hv_per_cpu_context *hv_cpu;
        u64 status;

        if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
                return -EMSGSIZE;

        hv_cpu = get_cpu_ptr(hv_context.cpu_context);
        aligned_msg = hv_cpu->post_msg_page;
        aligned_msg->connectionid = connection_id;
        aligned_msg->reserved = 0;
        aligned_msg->message_type = message_type;
        aligned_msg->payload_size = payload_size;
        memcpy((void *)aligned_msg->payload, payload, payload_size);

        status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL);

        /* Preemption must remain disabled until after the hypercall
         * so some other thread can't get scheduled onto this cpu and
         * corrupt the per-cpu post_msg_page
         */
        put_cpu_ptr(hv_cpu);

        return status & 0xFFFF;
}

/*
 * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
 * does not use VMbus or any VMbus messages, so process here and not
 * in the VMbus driver code.
 */

static void hv_stimer0_isr(void)
{
        struct hv_per_cpu_context *hv_cpu;

        hv_cpu = this_cpu_ptr(hv_context.cpu_context);
        hv_cpu->clk_evt->event_handler(hv_cpu->clk_evt);
        add_interrupt_randomness(stimer0_vector, 0);
}

static int hv_ce_set_next_event(unsigned long delta,
                                struct clock_event_device *evt)
{
        u64 current_tick;

        WARN_ON(!clockevent_state_oneshot(evt));

        current_tick = hyperv_cs->read(NULL);
        current_tick += delta;
        hv_init_timer(0, current_tick);
        return 0;
}

static int hv_ce_shutdown(struct clock_event_device *evt)
{
        hv_init_timer(0, 0);
        hv_init_timer_config(0, 0);
        if (direct_mode_enabled)
                hv_disable_stimer0_percpu_irq(stimer0_irq);

        return 0;
}

static int hv_ce_set_oneshot(struct clock_event_device *evt)
{
        union hv_stimer_config timer_cfg;

        timer_cfg.as_uint64 = 0;
        timer_cfg.enable = 1;
        timer_cfg.auto_enable = 1;
        if (direct_mode_enabled) {
                /*
                 * When it expires, the timer will directly interrupt
                 * on the specified hardware vector/IRQ.
                 */
                timer_cfg.direct_mode = 1;
                timer_cfg.apic_vector = stimer0_vector;
                hv_enable_stimer0_percpu_irq(stimer0_irq);
        } else {
                /*
                 * When it expires, the timer will generate a VMbus message,
                 * to be handled by the normal VMbus interrupt handler.
                 */
                timer_cfg.direct_mode = 0;
                timer_cfg.sintx = VMBUS_MESSAGE_SINT;
        }
        hv_init_timer_config(0, timer_cfg.as_uint64);
        return 0;
}

static void hv_init_clockevent_device(struct clock_event_device *dev, int cpu)
{
        dev->name = "Hyper-V clockevent";
        dev->features = CLOCK_EVT_FEAT_ONESHOT;
        dev->cpumask = cpumask_of(cpu);
        dev->rating = 1000;
        /*
         * Avoid settint dev->owner = THIS_MODULE deliberately as doing so will
         * result in clockevents_config_and_register() taking additional
         * references to the hv_vmbus module making it impossible to unload.
         */

        dev->set_state_shutdown = hv_ce_shutdown;
        dev->set_state_oneshot = hv_ce_set_oneshot;
        dev->set_next_event = hv_ce_set_next_event;
}


int hv_synic_alloc(void)
{
        int cpu;
        struct hv_per_cpu_context *hv_cpu;

        /*
         * First, zero all per-cpu memory areas so hv_synic_free() can
         * detect what memory has been allocated and cleanup properly
         * after any failures.
         */
        for_each_present_cpu(cpu) {
                hv_cpu = per_cpu_ptr(hv_context.cpu_context, cpu);
                memset(hv_cpu, 0, sizeof(*hv_cpu));
        }

        hv_context.hv_numa_map = kcalloc(nr_node_ids, sizeof(struct cpumask),
                                         GFP_KERNEL);
        if (hv_context.hv_numa_map == NULL) {
                pr_err("Unable to allocate NUMA map\n");
                goto err;
        }

        for_each_present_cpu(cpu) {
                hv_cpu = per_cpu_ptr(hv_context.cpu_context, cpu);

                tasklet_init(&hv_cpu->msg_dpc,
                             vmbus_on_msg_dpc, (unsigned long) hv_cpu);

                hv_cpu->clk_evt = kzalloc(sizeof(struct clock_event_device),
                                          GFP_KERNEL);
                if (hv_cpu->clk_evt == NULL) {
                        pr_err("Unable to allocate clock event device\n");
                        goto err;
                }
                hv_init_clockevent_device(hv_cpu->clk_evt, cpu);

                hv_cpu->synic_message_page =
                        (void *)get_zeroed_page(GFP_ATOMIC);
                if (hv_cpu->synic_message_page == NULL) {
                        pr_err("Unable to allocate SYNIC message page\n");
                        goto err;
                }

                hv_cpu->synic_event_page = (void *)get_zeroed_page(GFP_ATOMIC);
                if (hv_cpu->synic_event_page == NULL) {
                        pr_err("Unable to allocate SYNIC event page\n");
                        goto err;
                }

                hv_cpu->post_msg_page = (void *)get_zeroed_page(GFP_ATOMIC);
                if (hv_cpu->post_msg_page == NULL) {
                        pr_err("Unable to allocate post msg page\n");
                        goto err;
                }

                INIT_LIST_HEAD(&hv_cpu->chan_list);
        }

        if (direct_mode_enabled &&
            hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
                                hv_stimer0_isr))
                goto err;

        return 0;
err:
        /*
         * Any memory allocations that succeeded will be freed when
         * the caller cleans up by calling hv_synic_free()
         */
        return -ENOMEM;
}


void hv_synic_free(void)
{
        int cpu;

        for_each_present_cpu(cpu) {
                struct hv_per_cpu_context *hv_cpu
                        = per_cpu_ptr(hv_context.cpu_context, cpu);

                kfree(hv_cpu->clk_evt);
                free_page((unsigned long)hv_cpu->synic_event_page);
                free_page((unsigned long)hv_cpu->synic_message_page);
                free_page((unsigned long)hv_cpu->post_msg_page);
        }

        kfree(hv_context.hv_numa_map);
}

/*
 * hv_synic_init - Initialize the Synthetic Interrupt Controller.
 *
 * If it is already initialized by another entity (ie x2v shim), we need to
 * retrieve the initialized message and event pages.  Otherwise, we create and
 * initialize the message and event pages.
 */
int hv_synic_init(unsigned int cpu)
{
        struct hv_per_cpu_context *hv_cpu
                = per_cpu_ptr(hv_context.cpu_context, cpu);
        union hv_synic_simp simp;
        union hv_synic_siefp siefp;
        union hv_synic_sint shared_sint;
        union hv_synic_scontrol sctrl;

        /* Setup the Synic's message page */
        hv_get_simp(simp.as_uint64);
        simp.simp_enabled = 1;
        simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
                >> PAGE_SHIFT;

        hv_set_simp(simp.as_uint64);

        /* Setup the Synic's event page */
        hv_get_siefp(siefp.as_uint64);
        siefp.siefp_enabled = 1;
        siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
                >> PAGE_SHIFT;

        hv_set_siefp(siefp.as_uint64);

        /* Setup the shared SINT. */
        hv_get_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);

        shared_sint.vector = HYPERVISOR_CALLBACK_VECTOR;
        shared_sint.masked = false;
        if (ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED)
                shared_sint.auto_eoi = false;
        else
                shared_sint.auto_eoi = true;

        hv_set_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);

        /* Enable the global synic bit */
        hv_get_synic_state(sctrl.as_uint64);
        sctrl.enable = 1;

        hv_set_synic_state(sctrl.as_uint64);

        /*
         * Register the per-cpu clockevent source.
         */
        if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE)
                clockevents_config_and_register(hv_cpu->clk_evt,
                                                HV_TIMER_FREQUENCY,
                                                HV_MIN_DELTA_TICKS,
                                                HV_MAX_MAX_DELTA_TICKS);
        return 0;
}

/*
 * hv_synic_clockevents_cleanup - Cleanup clockevent devices
 */
void hv_synic_clockevents_cleanup(void)
{
        int cpu;

        if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
                return;

        if (direct_mode_enabled)
                hv_remove_stimer0_irq(stimer0_irq);

        for_each_present_cpu(cpu) {
                struct hv_per_cpu_context *hv_cpu
                        = per_cpu_ptr(hv_context.cpu_context, cpu);

                clockevents_unbind_device(hv_cpu->clk_evt, cpu);
        }
}

/*
 * hv_synic_cleanup - Cleanup routine for hv_synic_init().
 */
int hv_synic_cleanup(unsigned int cpu)
{
        union hv_synic_sint shared_sint;
        union hv_synic_simp simp;
        union hv_synic_siefp siefp;
        union hv_synic_scontrol sctrl;
        struct vmbus_channel *channel, *sc;
        bool channel_found = false;
        unsigned long flags;

        hv_get_synic_state(sctrl.as_uint64);
        if (sctrl.enable != 1)
                return -EFAULT;

        /*
         * Search for channels which are bound to the CPU we're about to
         * cleanup. In case we find one and vmbus is still connected we need to
         * fail, this will effectively prevent CPU offlining. There is no way
         * we can re-bind channels to different CPUs for now.
         */
        mutex_lock(&vmbus_connection.channel_mutex);
        list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
                if (channel->target_cpu == cpu) {
                        channel_found = true;
                        break;
                }
                spin_lock_irqsave(&channel->lock, flags);
                list_for_each_entry(sc, &channel->sc_list, sc_list) {
                        if (sc->target_cpu == cpu) {
                                channel_found = true;
                                break;
                        }
                }
                spin_unlock_irqrestore(&channel->lock, flags);
                if (channel_found)
                        break;
        }
        mutex_unlock(&vmbus_connection.channel_mutex);

        if (channel_found && vmbus_connection.conn_state == CONNECTED)
                return -EBUSY;

        /* Turn off clockevent device */
        if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
                struct hv_per_cpu_context *hv_cpu
                        = this_cpu_ptr(hv_context.cpu_context);

                clockevents_unbind_device(hv_cpu->clk_evt, cpu);
                hv_ce_shutdown(hv_cpu->clk_evt);
                put_cpu_ptr(hv_cpu);
        }

        hv_get_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);

        shared_sint.masked = 1;

        /* Need to correctly cleanup in the case of SMP!!! */
        /* Disable the interrupt */
        hv_set_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);

        hv_get_simp(simp.as_uint64);
        simp.simp_enabled = 0;
        simp.base_simp_gpa = 0;

        hv_set_simp(simp.as_uint64);

        hv_get_siefp(siefp.as_uint64);
        siefp.siefp_enabled = 0;
        siefp.base_siefp_gpa = 0;

        hv_set_siefp(siefp.as_uint64);

        /* Disable the global synic bit */
        sctrl.enable = 0;
        hv_set_synic_state(sctrl.as_uint64);

        return 0;
}