/*
 * vpt.c: Virtual Platform Timer
 *
 * Copyright (c) 2006, Xiaowei Yang, Intel 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, see <http://www.gnu.org/licenses/>.
 */

#include <xen/time.h>
#include <asm/hvm/support.h>
#include <asm/hvm/vpt.h>
#include <asm/event.h>
#include <asm/apic.h>
#include <asm/mc146818rtc.h>

#define mode_is(d, name) \
    ((d)->arch.hvm_domain.params[HVM_PARAM_TIMER_MODE] == HVMPTM_##name)

void hvm_init_guest_time(struct domain *d)
{
    struct pl_time *pl = d->arch.hvm_domain.pl_time;

    spin_lock_init(&pl->pl_time_lock);
    pl->stime_offset = -(u64)get_s_time();
    pl->last_guest_time = 0;
}

u64 hvm_get_guest_time_fixed(struct vcpu *v, u64 at_tsc)
{
    struct pl_time *pl = v->domain->arch.hvm_domain.pl_time;
    u64 now;

    /* Called from device models shared with PV guests. Be careful. */
    ASSERT(is_hvm_vcpu(v));

    spin_lock(&pl->pl_time_lock);
    now = get_s_time_fixed(at_tsc) + pl->stime_offset;

    if ( !at_tsc )
    {
        if ( (int64_t)(now - pl->last_guest_time) > 0 )
            pl->last_guest_time = now;
        else
            now = ++pl->last_guest_time;
    }
    spin_unlock(&pl->pl_time_lock);

    return now + v->arch.hvm_vcpu.stime_offset;
}

void hvm_set_guest_time(struct vcpu *v, u64 guest_time)
{
    u64 offset = guest_time - hvm_get_guest_time(v);

    if ( offset )
    {
        v->arch.hvm_vcpu.stime_offset += offset;
        /*
         * If hvm_vcpu.stime_offset is updated make sure to
         * also update vcpu time, since this value is used to
         * calculate the TSC.
         */
        if ( v == current )
            update_vcpu_system_time(v);
    }
}

static int pt_irq_vector(struct periodic_time *pt, enum hvm_intsrc src)
{
    struct vcpu *v = pt->vcpu;
    unsigned int gsi, isa_irq;

    if ( pt->source == PTSRC_lapic )
        return pt->irq;

    isa_irq = pt->irq;
    gsi = hvm_isa_irq_to_gsi(isa_irq);

    if ( src == hvm_intsrc_pic )
        return (v->domain->arch.hvm_domain.vpic[isa_irq >> 3].irq_base
                + (isa_irq & 7));

    ASSERT(src == hvm_intsrc_lapic);
    return domain_vioapic(v->domain)->redirtbl[gsi].fields.vector;
}

static int pt_irq_masked(struct periodic_time *pt)
{
    struct vcpu *v = pt->vcpu;
    unsigned int gsi = pt->irq;

    switch ( pt->source )
    {
    case PTSRC_lapic:
    {
        struct vlapic *vlapic = vcpu_vlapic(v);

        return (!vlapic_enabled(vlapic) ||
                (vlapic_get_reg(vlapic, APIC_LVTT) & APIC_LVT_MASKED));
    }

    case PTSRC_isa:
    {
        uint8_t pic_imr = v->domain->arch.hvm_domain.vpic[pt->irq >> 3].imr;

        /* Check if the interrupt is unmasked in the PIC. */
        if ( !(pic_imr & (1 << (pt->irq & 7))) && vlapic_accept_pic_intr(v) )
            return 0;

        gsi = hvm_isa_irq_to_gsi(pt->irq);
    }

    /* Fallthrough to check if the interrupt is masked on the IO APIC. */
    case PTSRC_ioapic:
        return domain_vioapic(v->domain)->redirtbl[gsi].fields.mask;
    }

    ASSERT_UNREACHABLE();
    return 1;
}

static void pt_lock(struct periodic_time *pt)
{
    struct vcpu *v;

    for ( ; ; )
    {
        v = pt->vcpu;
        spin_lock(&v->arch.hvm_vcpu.tm_lock);
        if ( likely(pt->vcpu == v) )
            break;
        spin_unlock(&v->arch.hvm_vcpu.tm_lock);
    }
}

static void pt_unlock(struct periodic_time *pt)
{
    spin_unlock(&pt->vcpu->arch.hvm_vcpu.tm_lock);
}

static void pt_process_missed_ticks(struct periodic_time *pt)
{
    s_time_t missed_ticks, now = NOW();

    if ( pt->one_shot )
        return;

    missed_ticks = now - pt->scheduled;
    if ( missed_ticks <= 0 )
        return;

    missed_ticks = missed_ticks / (s_time_t) pt->period + 1;
    if ( mode_is(pt->vcpu->domain, no_missed_ticks_pending) )
        pt->do_not_freeze = !pt->pending_intr_nr;
    else
        pt->pending_intr_nr += missed_ticks;
    pt->scheduled += missed_ticks * pt->period;
}

static void pt_freeze_time(struct vcpu *v)
{
    if ( !mode_is(v->domain, delay_for_missed_ticks) )
        return;

    v->arch.hvm_vcpu.guest_time = hvm_get_guest_time(v);
}

static void pt_thaw_time(struct vcpu *v)
{
    if ( !mode_is(v->domain, delay_for_missed_ticks) )
        return;

    if ( v->arch.hvm_vcpu.guest_time == 0 )
        return;

    hvm_set_guest_time(v, v->arch.hvm_vcpu.guest_time);
    v->arch.hvm_vcpu.guest_time = 0;
}

void pt_save_timer(struct vcpu *v)
{
    struct list_head *head = &v->arch.hvm_vcpu.tm_list;
    struct periodic_time *pt;

    if ( v->pause_flags & VPF_blocked )
        return;

    spin_lock(&v->arch.hvm_vcpu.tm_lock);

    list_for_each_entry ( pt, head, list )
        if ( !pt->do_not_freeze )
            stop_timer(&pt->timer);

    pt_freeze_time(v);

    spin_unlock(&v->arch.hvm_vcpu.tm_lock);
}

void pt_restore_timer(struct vcpu *v)
{
    struct list_head *head = &v->arch.hvm_vcpu.tm_list;
    struct periodic_time *pt;

    spin_lock(&v->arch.hvm_vcpu.tm_lock);

    list_for_each_entry ( pt, head, list )
    {
        if ( pt->pending_intr_nr == 0 )
        {
            pt_process_missed_ticks(pt);
            set_timer(&pt->timer, pt->scheduled);
        }
    }

    pt_thaw_time(v);

    spin_unlock(&v->arch.hvm_vcpu.tm_lock);
}

static void pt_timer_fn(void *data)
{
    struct periodic_time *pt = data;

    pt_lock(pt);

    pt->pending_intr_nr++;
    pt->scheduled += pt->period;
    pt->do_not_freeze = 0;

    vcpu_kick(pt->vcpu);

    pt_unlock(pt);
}

int pt_update_irq(struct vcpu *v)
{
    struct list_head *head = &v->arch.hvm_vcpu.tm_list;
    struct periodic_time *pt, *temp, *earliest_pt;
    uint64_t max_lag;
    int irq, pt_vector = -1;

    spin_lock(&v->arch.hvm_vcpu.tm_lock);

    earliest_pt = NULL;
    max_lag = -1ULL;
    list_for_each_entry_safe ( pt, temp, head, list )
    {
        if ( pt->pending_intr_nr )
        {
            /* RTC code takes care of disabling the timer itself. */
            if ( (pt->irq != RTC_IRQ || !pt->priv) && pt_irq_masked(pt) )
            {
                /* suspend timer emulation */
                list_del(&pt->list);
                pt->on_list = 0;
            }
            else
            {
                if ( (pt->last_plt_gtime + pt->period) < max_lag )
                {
                    max_lag = pt->last_plt_gtime + pt->period;
                    earliest_pt = pt;
                }
            }
        }
    }

    if ( earliest_pt == NULL )
    {
        spin_unlock(&v->arch.hvm_vcpu.tm_lock);
        return -1;
    }

    earliest_pt->irq_issued = 1;
    irq = earliest_pt->irq;

    spin_unlock(&v->arch.hvm_vcpu.tm_lock);

    switch ( earliest_pt->source )
    {
    case PTSRC_lapic:
        /*
         * If periodic timer interrupt is handled by lapic, its vector in
         * IRR is returned and used to set eoi_exit_bitmap for virtual
         * interrupt delivery case. Otherwise return -1 to do nothing.
         */
        vlapic_set_irq(vcpu_vlapic(v), irq, 0);
        pt_vector = irq;
        break;

    case PTSRC_isa:
        hvm_isa_irq_deassert(v->domain, irq);
        hvm_isa_irq_assert(v->domain, irq);

        if ( platform_legacy_irq(irq) && vlapic_accept_pic_intr(v) &&
             v->domain->arch.hvm_domain.vpic[irq >> 3].int_output )
            return -1;

        pt_vector = pt_irq_vector(earliest_pt, hvm_intsrc_lapic);
        break;

    case PTSRC_ioapic:
        /*
         * NB: At the moment IO-APIC routed interrupts generated by vpt devices
         * (HPET) are edge-triggered.
         */
        pt_vector = hvm_ioapic_assert(v->domain, irq, false);
        break;
    }

    return pt_vector;
}

static struct periodic_time *is_pt_irq(
    struct vcpu *v, struct hvm_intack intack)
{
    struct list_head *head = &v->arch.hvm_vcpu.tm_list;
    struct periodic_time *pt;

    list_for_each_entry ( pt, head, list )
    {
        if ( pt->pending_intr_nr && pt->irq_issued &&
             (intack.vector == pt_irq_vector(pt, intack.source)) )
            return pt;
    }

    return NULL;
}

void pt_intr_post(struct vcpu *v, struct hvm_intack intack)
{
    struct periodic_time *pt;
    time_cb *cb;
    void *cb_priv;

    if ( intack.source == hvm_intsrc_vector )
        return;

    spin_lock(&v->arch.hvm_vcpu.tm_lock);

    pt = is_pt_irq(v, intack);
    if ( pt == NULL )
    {
        spin_unlock(&v->arch.hvm_vcpu.tm_lock);
        return;
    }

    pt->irq_issued = 0;

    if ( pt->one_shot )
    {
        if ( pt->on_list )
            list_del(&pt->list);
        pt->on_list = 0;
        pt->pending_intr_nr = 0;
    }
    else if ( mode_is(v->domain, one_missed_tick_pending) ||
              mode_is(v->domain, no_missed_ticks_pending) )
    {
        pt->last_plt_gtime = hvm_get_guest_time(v);
        pt_process_missed_ticks(pt);
        pt->pending_intr_nr = 0; /* 'collapse' all missed ticks */
        set_timer(&pt->timer, pt->scheduled);
    }
    else
    {
        pt->last_plt_gtime += pt->period;
        if ( --pt->pending_intr_nr == 0 )
        {
            pt_process_missed_ticks(pt);
            if ( pt->pending_intr_nr == 0 )
                set_timer(&pt->timer, pt->scheduled);
        }
    }

    if ( mode_is(v->domain, delay_for_missed_ticks) &&
         (hvm_get_guest_time(v) < pt->last_plt_gtime) )
        hvm_set_guest_time(v, pt->last_plt_gtime);

    cb = pt->cb;
    cb_priv = pt->priv;

    spin_unlock(&v->arch.hvm_vcpu.tm_lock);

    if ( cb != NULL )
        cb(v, cb_priv);
}

void pt_migrate(struct vcpu *v)
{
    struct list_head *head = &v->arch.hvm_vcpu.tm_list;
    struct periodic_time *pt;

    spin_lock(&v->arch.hvm_vcpu.tm_lock);

    list_for_each_entry ( pt, head, list )
        migrate_timer(&pt->timer, v->processor);

    spin_unlock(&v->arch.hvm_vcpu.tm_lock);
}

void create_periodic_time(
    struct vcpu *v, struct periodic_time *pt, uint64_t delta,
    uint64_t period, uint8_t irq, time_cb *cb, void *data)
{
    if ( !pt->source ||
         (pt->irq >= NR_ISAIRQS && pt->source == PTSRC_isa) ||
         (pt->irq >= VIOAPIC_NUM_PINS && pt->source == PTSRC_ioapic) )
    {
        ASSERT_UNREACHABLE();
        return;
    }

    destroy_periodic_time(pt);

    spin_lock(&v->arch.hvm_vcpu.tm_lock);

    pt->pending_intr_nr = 0;
    pt->do_not_freeze = 0;
    pt->irq_issued = 0;

    /* Periodic timer must be at least 0.1ms. */
    if ( (period < 100000) && period )
    {
        if ( !test_and_set_bool(pt->warned_timeout_too_short) )
            gdprintk(XENLOG_WARNING, "HVM_PlatformTime: program too "
                     "small period %"PRIu64"\n", period);
        period = 100000;
    }

    pt->period = period;
    pt->vcpu = v;
    pt->last_plt_gtime = hvm_get_guest_time(pt->vcpu);
    pt->irq = irq;
    pt->one_shot = !period;
    pt->scheduled = NOW() + delta;

    if ( !pt->one_shot )
    {
        if ( v->domain->arch.hvm_domain.params[HVM_PARAM_VPT_ALIGN] )
        {
            pt->scheduled = align_timer(pt->scheduled, pt->period);
        }
        else if ( pt->source == PTSRC_lapic )
        {
            /*
             * Offset LAPIC ticks from other timer ticks. Otherwise guests
             * which use LAPIC ticks for process accounting can see long
             * sequences of process ticks incorrectly accounted to interrupt
             * processing (seen with RHEL3 guest).
             */
            pt->scheduled += delta >> 1;
        }
    }

    pt->cb = cb;
    pt->priv = data;

    pt->on_list = 1;
    list_add(&pt->list, &v->arch.hvm_vcpu.tm_list);

    init_timer(&pt->timer, pt_timer_fn, pt, v->processor);
    set_timer(&pt->timer, pt->scheduled);

    spin_unlock(&v->arch.hvm_vcpu.tm_lock);
}

void destroy_periodic_time(struct periodic_time *pt)
{
    /* Was this structure previously initialised by create_periodic_time()? */
    if ( pt->vcpu == NULL )
        return;

    pt_lock(pt);
    if ( pt->on_list )
        list_del(&pt->list);
    pt->on_list = 0;
    pt->pending_intr_nr = 0;
    pt_unlock(pt);

    /*
     * pt_timer_fn() can run until this kill_timer() returns. We must do this
     * outside pt_lock() otherwise we can deadlock with pt_timer_fn().
     */
    kill_timer(&pt->timer);
}

static void pt_adjust_vcpu(struct periodic_time *pt, struct vcpu *v)
{
    int on_list;

    ASSERT(pt->source == PTSRC_isa || pt->source == PTSRC_ioapic);

    if ( pt->vcpu == NULL )
        return;

    pt_lock(pt);
    on_list = pt->on_list;
    if ( pt->on_list )
        list_del(&pt->list);
    pt->on_list = 0;
    pt_unlock(pt);

    spin_lock(&v->arch.hvm_vcpu.tm_lock);
    pt->vcpu = v;
    if ( on_list )
    {
        pt->on_list = 1;
        list_add(&pt->list, &v->arch.hvm_vcpu.tm_list);

        migrate_timer(&pt->timer, v->processor);
    }
    spin_unlock(&v->arch.hvm_vcpu.tm_lock);
}

void pt_adjust_global_vcpu_target(struct vcpu *v)
{
    struct PITState *vpit;
    struct pl_time *pl_time;
    int i;

    if ( !v || !has_vpit(v->domain) )
        return;

    vpit = &v->domain->arch.vpit;

    spin_lock(&vpit->lock);
    pt_adjust_vcpu(&vpit->pt0, v);
    spin_unlock(&vpit->lock);

    pl_time = v->domain->arch.hvm_domain.pl_time;

    spin_lock(&pl_time->vrtc.lock);
    pt_adjust_vcpu(&pl_time->vrtc.pt, v);
    spin_unlock(&pl_time->vrtc.lock);

    write_lock(&pl_time->vhpet.lock);
    for ( i = 0; i < HPET_TIMER_NUM; i++ )
        pt_adjust_vcpu(&pl_time->vhpet.pt[i], v);
    write_unlock(&pl_time->vhpet.lock);
}


static void pt_resume(struct periodic_time *pt)
{
    if ( pt->vcpu == NULL )
        return;

    pt_lock(pt);
    if ( pt->pending_intr_nr && !pt->on_list )
    {
        pt->on_list = 1;
        list_add(&pt->list, &pt->vcpu->arch.hvm_vcpu.tm_list);
        vcpu_kick(pt->vcpu);
    }
    pt_unlock(pt);
}

void pt_may_unmask_irq(struct domain *d, struct periodic_time *vlapic_pt)
{
    int i;

    if ( d )
    {
        pt_resume(&d->arch.vpit.pt0);
        pt_resume(&d->arch.hvm_domain.pl_time->vrtc.pt);
        for ( i = 0; i < HPET_TIMER_NUM; i++ )
            pt_resume(&d->arch.hvm_domain.pl_time->vhpet.pt[i]);
    }

    if ( vlapic_pt )
        pt_resume(vlapic_pt);
}
