/*
 * Copyright (C) 2012 ARM Ltd.
 * Author: Marc Zyngier <marc.zyngier@arm.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that 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
 */

#include <linux/cpu.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/uaccess.h>

#include <clocksource/arm_arch_timer.h>
#include <asm/arch_timer.h>
#include <asm/kvm_hyp.h>

#include <kvm/arm_vgic.h>
#include <kvm/arm_arch_timer.h>

#include "trace.h"

static struct timecounter *timecounter;
static unsigned int host_vtimer_irq;
static u32 host_vtimer_irq_flags;

static DEFINE_STATIC_KEY_FALSE(has_gic_active_state);

static const struct kvm_irq_level default_ptimer_irq = {
        .irq    = 30,
        .level  = 1,
};

static const struct kvm_irq_level default_vtimer_irq = {
        .irq    = 27,
        .level  = 1,
};

static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx);
static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
                                 struct arch_timer_context *timer_ctx);
static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx);

u64 kvm_phys_timer_read(void)
{
        return timecounter->cc->read(timecounter->cc);
}

static inline bool userspace_irqchip(struct kvm *kvm)
{
        return static_branch_unlikely(&userspace_irqchip_in_use) &&
                unlikely(!irqchip_in_kernel(kvm));
}

static void soft_timer_start(struct hrtimer *hrt, u64 ns)
{
        hrtimer_start(hrt, ktime_add_ns(ktime_get(), ns),
                      HRTIMER_MODE_ABS);
}

static void soft_timer_cancel(struct hrtimer *hrt, struct work_struct *work)
{
        hrtimer_cancel(hrt);
        if (work)
                cancel_work_sync(work);
}

static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
{
        struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)dev_id;
        struct arch_timer_context *vtimer;

        /*
         * We may see a timer interrupt after vcpu_put() has been called which
         * sets the CPU's vcpu pointer to NULL, because even though the timer
         * has been disabled in vtimer_save_state(), the hardware interrupt
         * signal may not have been retired from the interrupt controller yet.
         */
        if (!vcpu)
                return IRQ_HANDLED;

        vtimer = vcpu_vtimer(vcpu);
        if (kvm_timer_should_fire(vtimer))
                kvm_timer_update_irq(vcpu, true, vtimer);

        if (userspace_irqchip(vcpu->kvm) &&
            !static_branch_unlikely(&has_gic_active_state))
                disable_percpu_irq(host_vtimer_irq);

        return IRQ_HANDLED;
}

/*
 * Work function for handling the backup timer that we schedule when a vcpu is
 * no longer running, but had a timer programmed to fire in the future.
 */
static void kvm_timer_inject_irq_work(struct work_struct *work)
{
        struct kvm_vcpu *vcpu;

        vcpu = container_of(work, struct kvm_vcpu, arch.timer_cpu.expired);

        /*
         * If the vcpu is blocked we want to wake it up so that it will see
         * the timer has expired when entering the guest.
         */
        kvm_vcpu_wake_up(vcpu);
}

static u64 kvm_timer_compute_delta(struct arch_timer_context *timer_ctx)
{
        u64 cval, now;

        cval = timer_ctx->cnt_cval;
        now = kvm_phys_timer_read() - timer_ctx->cntvoff;

        if (now < cval) {
                u64 ns;

                ns = cyclecounter_cyc2ns(timecounter->cc,
                                         cval - now,
                                         timecounter->mask,
                                         &timecounter->frac);
                return ns;
        }

        return 0;
}

static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx)
{
        return !(timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_IT_MASK) &&
                (timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_ENABLE);
}

/*
 * Returns the earliest expiration time in ns among guest timers.
 * Note that it will return 0 if none of timers can fire.
 */
static u64 kvm_timer_earliest_exp(struct kvm_vcpu *vcpu)
{
        u64 min_virt = ULLONG_MAX, min_phys = ULLONG_MAX;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);

        if (kvm_timer_irq_can_fire(vtimer))
                min_virt = kvm_timer_compute_delta(vtimer);

        if (kvm_timer_irq_can_fire(ptimer))
                min_phys = kvm_timer_compute_delta(ptimer);

        /* If none of timers can fire, then return 0 */
        if ((min_virt == ULLONG_MAX) && (min_phys == ULLONG_MAX))
                return 0;

        return min(min_virt, min_phys);
}

static enum hrtimer_restart kvm_bg_timer_expire(struct hrtimer *hrt)
{
        struct arch_timer_cpu *timer;
        struct kvm_vcpu *vcpu;
        u64 ns;

        timer = container_of(hrt, struct arch_timer_cpu, bg_timer);
        vcpu = container_of(timer, struct kvm_vcpu, arch.timer_cpu);

        /*
         * Check that the timer has really expired from the guest's
         * PoV (NTP on the host may have forced it to expire
         * early). If we should have slept longer, restart it.
         */
        ns = kvm_timer_earliest_exp(vcpu);
        if (unlikely(ns)) {
                hrtimer_forward_now(hrt, ns_to_ktime(ns));
                return HRTIMER_RESTART;
        }

        schedule_work(&timer->expired);
        return HRTIMER_NORESTART;
}

static enum hrtimer_restart kvm_phys_timer_expire(struct hrtimer *hrt)
{
        struct arch_timer_context *ptimer;
        struct arch_timer_cpu *timer;
        struct kvm_vcpu *vcpu;
        u64 ns;

        timer = container_of(hrt, struct arch_timer_cpu, phys_timer);
        vcpu = container_of(timer, struct kvm_vcpu, arch.timer_cpu);
        ptimer = vcpu_ptimer(vcpu);

        /*
         * Check that the timer has really expired from the guest's
         * PoV (NTP on the host may have forced it to expire
         * early). If not ready, schedule for a later time.
         */
        ns = kvm_timer_compute_delta(ptimer);
        if (unlikely(ns)) {
                hrtimer_forward_now(hrt, ns_to_ktime(ns));
                return HRTIMER_RESTART;
        }

        kvm_timer_update_irq(vcpu, true, ptimer);
        return HRTIMER_NORESTART;
}

static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx)
{
        u64 cval, now;

        if (timer_ctx->loaded) {
                u32 cnt_ctl;

                /* Only the virtual timer can be loaded so far */
                cnt_ctl = read_sysreg_el0(cntv_ctl);
                return  (cnt_ctl & ARCH_TIMER_CTRL_ENABLE) &&
                        (cnt_ctl & ARCH_TIMER_CTRL_IT_STAT) &&
                       !(cnt_ctl & ARCH_TIMER_CTRL_IT_MASK);
        }

        if (!kvm_timer_irq_can_fire(timer_ctx))
                return false;

        cval = timer_ctx->cnt_cval;
        now = kvm_phys_timer_read() - timer_ctx->cntvoff;

        return cval <= now;
}

bool kvm_timer_is_pending(struct kvm_vcpu *vcpu)
{
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);

        if (kvm_timer_should_fire(vtimer))
                return true;

        return kvm_timer_should_fire(ptimer);
}

/*
 * Reflect the timer output level into the kvm_run structure
 */
void kvm_timer_update_run(struct kvm_vcpu *vcpu)
{
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
        struct kvm_sync_regs *regs = &vcpu->run->s.regs;

        /* Populate the device bitmap with the timer states */
        regs->device_irq_level &= ~(KVM_ARM_DEV_EL1_VTIMER |
                                    KVM_ARM_DEV_EL1_PTIMER);
        if (kvm_timer_should_fire(vtimer))
                regs->device_irq_level |= KVM_ARM_DEV_EL1_VTIMER;
        if (kvm_timer_should_fire(ptimer))
                regs->device_irq_level |= KVM_ARM_DEV_EL1_PTIMER;
}

static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
                                 struct arch_timer_context *timer_ctx)
{
        int ret;

        timer_ctx->irq.level = new_level;
        trace_kvm_timer_update_irq(vcpu->vcpu_id, timer_ctx->irq.irq,
                                   timer_ctx->irq.level);

        if (!userspace_irqchip(vcpu->kvm)) {
                ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
                                          timer_ctx->irq.irq,
                                          timer_ctx->irq.level,
                                          timer_ctx);
                WARN_ON(ret);
        }
}

/* Schedule the background timer for the emulated timer. */
static void phys_timer_emulate(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);

        /*
         * If the timer can fire now we have just raised the IRQ line and we
         * don't need to have a soft timer scheduled for the future.  If the
         * timer cannot fire at all, then we also don't need a soft timer.
         */
        if (kvm_timer_should_fire(ptimer) || !kvm_timer_irq_can_fire(ptimer)) {
                soft_timer_cancel(&timer->phys_timer, NULL);
                return;
        }

        soft_timer_start(&timer->phys_timer, kvm_timer_compute_delta(ptimer));
}

/*
 * Check if there was a change in the timer state, so that we should either
 * raise or lower the line level to the GIC or schedule a background timer to
 * emulate the physical timer.
 */
static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
        bool level;

        if (unlikely(!timer->enabled))
                return;

        /*
         * The vtimer virtual interrupt is a 'mapped' interrupt, meaning part
         * of its lifecycle is offloaded to the hardware, and we therefore may
         * not have lowered the irq.level value before having to signal a new
         * interrupt, but have to signal an interrupt every time the level is
         * asserted.
         */
        level = kvm_timer_should_fire(vtimer);
        kvm_timer_update_irq(vcpu, level, vtimer);

        if (kvm_timer_should_fire(ptimer) != ptimer->irq.level)
                kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer);

        phys_timer_emulate(vcpu);
}

static void vtimer_save_state(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        unsigned long flags;

        local_irq_save(flags);

        if (!vtimer->loaded)
                goto out;

        if (timer->enabled) {
                vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
                vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
        }

        /* Disable the virtual timer */
        write_sysreg_el0(0, cntv_ctl);
        isb();

        vtimer->loaded = false;
out:
        local_irq_restore(flags);
}

/*
 * Schedule the background timer before calling kvm_vcpu_block, so that this
 * thread is removed from its waitqueue and made runnable when there's a timer
 * interrupt to handle.
 */
void kvm_timer_schedule(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);

        vtimer_save_state(vcpu);

        /*
         * No need to schedule a background timer if any guest timer has
         * already expired, because kvm_vcpu_block will return before putting
         * the thread to sleep.
         */
        if (kvm_timer_should_fire(vtimer) || kvm_timer_should_fire(ptimer))
                return;

        /*
         * If both timers are not capable of raising interrupts (disabled or
         * masked), then there's no more work for us to do.
         */
        if (!kvm_timer_irq_can_fire(vtimer) && !kvm_timer_irq_can_fire(ptimer))
                return;

        /*
         * The guest timers have not yet expired, schedule a background timer.
         * Set the earliest expiration time among the guest timers.
         */
        soft_timer_start(&timer->bg_timer, kvm_timer_earliest_exp(vcpu));
}

static void vtimer_restore_state(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        unsigned long flags;

        local_irq_save(flags);

        if (vtimer->loaded)
                goto out;

        if (timer->enabled) {
                write_sysreg_el0(vtimer->cnt_cval, cntv_cval);
                isb();
                write_sysreg_el0(vtimer->cnt_ctl, cntv_ctl);
        }

        vtimer->loaded = true;
out:
        local_irq_restore(flags);
}

void kvm_timer_unschedule(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

        vtimer_restore_state(vcpu);

        soft_timer_cancel(&timer->bg_timer, &timer->expired);
}

static void set_cntvoff(u64 cntvoff)
{
        u32 low = lower_32_bits(cntvoff);
        u32 high = upper_32_bits(cntvoff);

        /*
         * Since kvm_call_hyp doesn't fully support the ARM PCS especially on
         * 32-bit systems, but rather passes register by register shifted one
         * place (we put the function address in r0/x0), we cannot simply pass
         * a 64-bit value as an argument, but have to split the value in two
         * 32-bit halves.
         */
        kvm_call_hyp(__kvm_timer_set_cntvoff, low, high);
}

static inline void set_vtimer_irq_phys_active(struct kvm_vcpu *vcpu, bool active)
{
        int r;
        r = irq_set_irqchip_state(host_vtimer_irq, IRQCHIP_STATE_ACTIVE, active);
        WARN_ON(r);
}

static void kvm_timer_vcpu_load_gic(struct kvm_vcpu *vcpu)
{
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        bool phys_active;

        if (irqchip_in_kernel(vcpu->kvm))
                phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
        else
                phys_active = vtimer->irq.level;
        set_vtimer_irq_phys_active(vcpu, phys_active);
}

static void kvm_timer_vcpu_load_nogic(struct kvm_vcpu *vcpu)
{
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);

        /*
         * When using a userspace irqchip with the architected timers and a
         * host interrupt controller that doesn't support an active state, we
         * must still prevent continuously exiting from the guest, and
         * therefore mask the physical interrupt by disabling it on the host
         * interrupt controller when the virtual level is high, such that the
         * guest can make forward progress.  Once we detect the output level
         * being de-asserted, we unmask the interrupt again so that we exit
         * from the guest when the timer fires.
         */
        if (vtimer->irq.level)
                disable_percpu_irq(host_vtimer_irq);
        else
                enable_percpu_irq(host_vtimer_irq, host_vtimer_irq_flags);
}

void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);

        if (unlikely(!timer->enabled))
                return;

        if (static_branch_likely(&has_gic_active_state))
                kvm_timer_vcpu_load_gic(vcpu);
        else
                kvm_timer_vcpu_load_nogic(vcpu);

        set_cntvoff(vtimer->cntvoff);

        vtimer_restore_state(vcpu);

        /* Set the background timer for the physical timer emulation. */
        phys_timer_emulate(vcpu);
}

bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu)
{
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
        struct kvm_sync_regs *sregs = &vcpu->run->s.regs;
        bool vlevel, plevel;

        if (likely(irqchip_in_kernel(vcpu->kvm)))
                return false;

        vlevel = sregs->device_irq_level & KVM_ARM_DEV_EL1_VTIMER;
        plevel = sregs->device_irq_level & KVM_ARM_DEV_EL1_PTIMER;

        return kvm_timer_should_fire(vtimer) != vlevel ||
               kvm_timer_should_fire(ptimer) != plevel;
}

void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

        if (unlikely(!timer->enabled))
                return;

        vtimer_save_state(vcpu);

        /*
         * Cancel the physical timer emulation, because the only case where we
         * need it after a vcpu_put is in the context of a sleeping VCPU, and
         * in that case we already factor in the deadline for the physical
         * timer when scheduling the bg_timer.
         *
         * In any case, we re-schedule the hrtimer for the physical timer when
         * coming back to the VCPU thread in kvm_timer_vcpu_load().
         */
        soft_timer_cancel(&timer->phys_timer, NULL);

        /*
         * The kernel may decide to run userspace after calling vcpu_put, so
         * we reset cntvoff to 0 to ensure a consistent read between user
         * accesses to the virtual counter and kernel access to the physical
         * counter of non-VHE case. For VHE, the virtual counter uses a fixed
         * virtual offset of zero, so no need to zero CNTVOFF_EL2 register.
         */
        if (!has_vhe())
                set_cntvoff(0);
}

/*
 * With a userspace irqchip we have to check if the guest de-asserted the
 * timer and if so, unmask the timer irq signal on the host interrupt
 * controller to ensure that we see future timer signals.
 */
static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
{
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);

        if (!kvm_timer_should_fire(vtimer)) {
                kvm_timer_update_irq(vcpu, false, vtimer);
                if (static_branch_likely(&has_gic_active_state))
                        set_vtimer_irq_phys_active(vcpu, false);
                else
                        enable_percpu_irq(host_vtimer_irq, host_vtimer_irq_flags);
        }
}

void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

        if (unlikely(!timer->enabled))
                return;

        if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
                unmask_vtimer_irq_user(vcpu);
}

int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);

        /*
         * The bits in CNTV_CTL are architecturally reset to UNKNOWN for ARMv8
         * and to 0 for ARMv7.  We provide an implementation that always
         * resets the timer to be disabled and unmasked and is compliant with
         * the ARMv7 architecture.
         */
        vtimer->cnt_ctl = 0;
        ptimer->cnt_ctl = 0;
        kvm_timer_update_state(vcpu);

        if (timer->enabled && irqchip_in_kernel(vcpu->kvm))
                kvm_vgic_reset_mapped_irq(vcpu, vtimer->irq.irq);

        return 0;
}

/* Make the updates of cntvoff for all vtimer contexts atomic */
static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
{
        int i;
        struct kvm *kvm = vcpu->kvm;
        struct kvm_vcpu *tmp;

        mutex_lock(&kvm->lock);
        kvm_for_each_vcpu(i, tmp, kvm)
                vcpu_vtimer(tmp)->cntvoff = cntvoff;

        /*
         * When called from the vcpu create path, the CPU being created is not
         * included in the loop above, so we just set it here as well.
         */
        vcpu_vtimer(vcpu)->cntvoff = cntvoff;
        mutex_unlock(&kvm->lock);
}

void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);

        /* Synchronize cntvoff across all vtimers of a VM. */
        update_vtimer_cntvoff(vcpu, kvm_phys_timer_read());
        vcpu_ptimer(vcpu)->cntvoff = 0;

        INIT_WORK(&timer->expired, kvm_timer_inject_irq_work);
        hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
        timer->bg_timer.function = kvm_bg_timer_expire;

        hrtimer_init(&timer->phys_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
        timer->phys_timer.function = kvm_phys_timer_expire;

        vtimer->irq.irq = default_vtimer_irq.irq;
        ptimer->irq.irq = default_ptimer_irq.irq;
}

static void kvm_timer_init_interrupt(void *info)
{
        enable_percpu_irq(host_vtimer_irq, host_vtimer_irq_flags);
}

int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
{
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);

        switch (regid) {
        case KVM_REG_ARM_TIMER_CTL:
                vtimer->cnt_ctl = value & ~ARCH_TIMER_CTRL_IT_STAT;
                break;
        case KVM_REG_ARM_TIMER_CNT:
                update_vtimer_cntvoff(vcpu, kvm_phys_timer_read() - value);
                break;
        case KVM_REG_ARM_TIMER_CVAL:
                vtimer->cnt_cval = value;
                break;
        case KVM_REG_ARM_PTIMER_CTL:
                ptimer->cnt_ctl = value & ~ARCH_TIMER_CTRL_IT_STAT;
                break;
        case KVM_REG_ARM_PTIMER_CVAL:
                ptimer->cnt_cval = value;
                break;

        default:
                return -1;
        }

        kvm_timer_update_state(vcpu);
        return 0;
}

static u64 read_timer_ctl(struct arch_timer_context *timer)
{
        /*
         * Set ISTATUS bit if it's expired.
         * Note that according to ARMv8 ARM Issue A.k, ISTATUS bit is
         * UNKNOWN when ENABLE bit is 0, so we chose to set ISTATUS bit
         * regardless of ENABLE bit for our implementation convenience.
         */
        if (!kvm_timer_compute_delta(timer))
                return timer->cnt_ctl | ARCH_TIMER_CTRL_IT_STAT;
        else
                return timer->cnt_ctl;
}

u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
{
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);

        switch (regid) {
        case KVM_REG_ARM_TIMER_CTL:
                return read_timer_ctl(vtimer);
        case KVM_REG_ARM_TIMER_CNT:
                return kvm_phys_timer_read() - vtimer->cntvoff;
        case KVM_REG_ARM_TIMER_CVAL:
                return vtimer->cnt_cval;
        case KVM_REG_ARM_PTIMER_CTL:
                return read_timer_ctl(ptimer);
        case KVM_REG_ARM_PTIMER_CVAL:
                return ptimer->cnt_cval;
        case KVM_REG_ARM_PTIMER_CNT:
                return kvm_phys_timer_read();
        }
        return (u64)-1;
}

static int kvm_timer_starting_cpu(unsigned int cpu)
{
        kvm_timer_init_interrupt(NULL);
        return 0;
}

static int kvm_timer_dying_cpu(unsigned int cpu)
{
        disable_percpu_irq(host_vtimer_irq);
        return 0;
}

int kvm_timer_hyp_init(bool has_gic)
{
        struct arch_timer_kvm_info *info;
        int err;

        info = arch_timer_get_kvm_info();
        timecounter = &info->timecounter;

        if (!timecounter->cc) {
                kvm_err("kvm_arch_timer: uninitialized timecounter\n");
                return -ENODEV;
        }

        if (info->virtual_irq <= 0) {
                kvm_err("kvm_arch_timer: invalid virtual timer IRQ: %d\n",
                        info->virtual_irq);
                return -ENODEV;
        }
        host_vtimer_irq = info->virtual_irq;

        host_vtimer_irq_flags = irq_get_trigger_type(host_vtimer_irq);
        if (host_vtimer_irq_flags != IRQF_TRIGGER_HIGH &&
            host_vtimer_irq_flags != IRQF_TRIGGER_LOW) {
                kvm_err("Invalid trigger for IRQ%d, assuming level low\n",
                        host_vtimer_irq);
                host_vtimer_irq_flags = IRQF_TRIGGER_LOW;
        }

        err = request_percpu_irq(host_vtimer_irq, kvm_arch_timer_handler,
                                 "kvm guest timer", kvm_get_running_vcpus());
        if (err) {
                kvm_err("kvm_arch_timer: can't request interrupt %d (%d)\n",
                        host_vtimer_irq, err);
                return err;
        }

        if (has_gic) {
                err = irq_set_vcpu_affinity(host_vtimer_irq,
                                            kvm_get_running_vcpus());
                if (err) {
                        kvm_err("kvm_arch_timer: error setting vcpu affinity\n");
                        goto out_free_irq;
                }

                static_branch_enable(&has_gic_active_state);
        }

        kvm_debug("virtual timer IRQ%d\n", host_vtimer_irq);

        cpuhp_setup_state(CPUHP_AP_KVM_ARM_TIMER_STARTING,
                          "kvm/arm/timer:starting", kvm_timer_starting_cpu,
                          kvm_timer_dying_cpu);
        return 0;
out_free_irq:
        free_percpu_irq(host_vtimer_irq, kvm_get_running_vcpus());
        return err;
}

void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);

        soft_timer_cancel(&timer->bg_timer, &timer->expired);
        soft_timer_cancel(&timer->phys_timer, NULL);
        kvm_vgic_unmap_phys_irq(vcpu, vtimer->irq.irq);
}

static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
{
        int vtimer_irq, ptimer_irq;
        int i, ret;

        vtimer_irq = vcpu_vtimer(vcpu)->irq.irq;
        ret = kvm_vgic_set_owner(vcpu, vtimer_irq, vcpu_vtimer(vcpu));
        if (ret)
                return false;

        ptimer_irq = vcpu_ptimer(vcpu)->irq.irq;
        ret = kvm_vgic_set_owner(vcpu, ptimer_irq, vcpu_ptimer(vcpu));
        if (ret)
                return false;

        kvm_for_each_vcpu(i, vcpu, vcpu->kvm) {
                if (vcpu_vtimer(vcpu)->irq.irq != vtimer_irq ||
                    vcpu_ptimer(vcpu)->irq.irq != ptimer_irq)
                        return false;
        }

        return true;
}

bool kvm_arch_timer_get_input_level(int vintid)
{
        struct kvm_vcpu *vcpu = kvm_arm_get_running_vcpu();
        struct arch_timer_context *timer;

        if (vintid == vcpu_vtimer(vcpu)->irq.irq)
                timer = vcpu_vtimer(vcpu);
        else
                BUG(); /* We only map the vtimer so far */

        return kvm_timer_should_fire(timer);
}

int kvm_timer_enable(struct kvm_vcpu *vcpu)
{
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        int ret;

        if (timer->enabled)
                return 0;

        /* Without a VGIC we do not map virtual IRQs to physical IRQs */
        if (!irqchip_in_kernel(vcpu->kvm))
                goto no_vgic;

        if (!vgic_initialized(vcpu->kvm))
                return -ENODEV;

        if (!timer_irqs_are_valid(vcpu)) {
                kvm_debug("incorrectly configured timer irqs\n");
                return -EINVAL;
        }

        ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
                                    kvm_arch_timer_get_input_level);
        if (ret)
                return ret;

no_vgic:
        timer->enabled = 1;
        return 0;
}

/*
 * On VHE system, we only need to configure trap on physical timer and counter
 * accesses in EL0 and EL1 once, not for every world switch.
 * The host kernel runs at EL2 with HCR_EL2.TGE == 1,
 * and this makes those bits have no effect for the host kernel execution.
 */
void kvm_timer_init_vhe(void)
{
        /* When HCR_EL2.E2H ==1, EL1PCEN and EL1PCTEN are shifted by 10 */
        u32 cnthctl_shift = 10;
        u64 val;

        /*
         * Disallow physical timer access for the guest.
         * Physical counter access is allowed.
         */
        val = read_sysreg(cnthctl_el2);
        val &= ~(CNTHCTL_EL1PCEN << cnthctl_shift);
        val |= (CNTHCTL_EL1PCTEN << cnthctl_shift);
        write_sysreg(val, cnthctl_el2);
}

static void set_timer_irqs(struct kvm *kvm, int vtimer_irq, int ptimer_irq)
{
        struct kvm_vcpu *vcpu;
        int i;

        kvm_for_each_vcpu(i, vcpu, kvm) {
                vcpu_vtimer(vcpu)->irq.irq = vtimer_irq;
                vcpu_ptimer(vcpu)->irq.irq = ptimer_irq;
        }
}

int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
        int __user *uaddr = (int __user *)(long)attr->addr;
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
        int irq;

        if (!irqchip_in_kernel(vcpu->kvm))
                return -EINVAL;

        if (get_user(irq, uaddr))
                return -EFAULT;

        if (!(irq_is_ppi(irq)))
                return -EINVAL;

        if (vcpu->arch.timer_cpu.enabled)
                return -EBUSY;

        switch (attr->attr) {
        case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
                set_timer_irqs(vcpu->kvm, irq, ptimer->irq.irq);
                break;
        case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
                set_timer_irqs(vcpu->kvm, vtimer->irq.irq, irq);
                break;
        default:
                return -ENXIO;
        }

        return 0;
}

int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
        int __user *uaddr = (int __user *)(long)attr->addr;
        struct arch_timer_context *timer;
        int irq;

        switch (attr->attr) {
        case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
                timer = vcpu_vtimer(vcpu);
                break;
        case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
                timer = vcpu_ptimer(vcpu);
                break;
        default:
                return -ENXIO;
        }

        irq = timer->irq.irq;
        return put_user(irq, uaddr);
}

int kvm_arm_timer_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
        switch (attr->attr) {
        case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
        case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
                return 0;
        }

        return -ENXIO;
}