virt/kvm/arm/arch_timer.c - kernel/msm-4.19 - Gitiles

 /*
  * 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/of_irq.h>
 #include <linux/kvm.h>
 #include <linux/kvm_host.h>
 #include <linux/interrupt.h>

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

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

 static struct timecounter *timecounter;
 static struct workqueue_struct *wqueue;
 static unsigned int host_vtimer_irq;

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

 static bool timer_is_armed(struct arch_timer_cpu *timer)
 {
 	return timer->armed;
 }

 /* timer_arm: as in "arm the timer", not as in ARM the company */
 static void timer_arm(struct arch_timer_cpu *timer, u64 ns)
 {
 	timer->armed = true;
 	hrtimer_start(&timer->timer, ktime_add_ns(ktime_get(), ns),
 		      HRTIMER_MODE_ABS);
 }

 static void timer_disarm(struct arch_timer_cpu *timer)
 {
 	if (timer_is_armed(timer)) {
 		hrtimer_cancel(&timer->timer);
 		cancel_work_sync(&timer->expired);
 		timer->armed = false;
 	}
 }

 static void kvm_timer_inject_irq(struct kvm_vcpu *vcpu)
 {
 	int ret;
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

 	kvm_vgic_set_phys_irq_active(timer->map, true);
 	ret = kvm_vgic_inject_mapped_irq(vcpu->kvm, vcpu->vcpu_id,
 					 timer->map,
 					 timer->irq->level);
 	WARN_ON(ret);
 }

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

 	/*
 	 * We disable the timer in the world switch and let it be
 	 * handled by kvm_timer_sync_hwstate(). Getting a timer
 	 * interrupt at this point is a sure sign of some major
 	 * breakage.
 	 */
 	pr_warn("Unexpected interrupt %d on vcpu %p\n", irq, vcpu);
 	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);
 	vcpu->arch.timer_cpu.armed = false;

 	/*
 	 * 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_kick(vcpu);
 }

 static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
 {
 	struct arch_timer_cpu *timer;
 	timer = container_of(hrt, struct arch_timer_cpu, timer);
 	queue_work(wqueue, &timer->expired);
 	return HRTIMER_NORESTART;
 }

 bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 	cycle_t cval, now;

 	if ((timer->cntv_ctl & ARCH_TIMER_CTRL_IT_MASK) ||
 	    !(timer->cntv_ctl & ARCH_TIMER_CTRL_ENABLE) ||
 	    kvm_vgic_get_phys_irq_active(timer->map))
 		return false;

 	cval = timer->cntv_cval;
 	now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;

 	return cval <= now;
 }

 /**
  * kvm_timer_flush_hwstate - prepare to move the virt timer to the cpu
  * @vcpu: The vcpu pointer
  *
  * Disarm any pending soft timers, since the world-switch code will write the
  * virtual timer state back to the physical CPU.
  */
 void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

 	/*
 	 * We're about to run this vcpu again, so there is no need to
 	 * keep the background timer running, as we're about to
 	 * populate the CPU timer again.
 	 */
 	timer_disarm(timer);

 	/*
 	 * If the timer expired while we were not scheduled, now is the time
 	 * to inject it.
 	 */
 	if (kvm_timer_should_fire(vcpu))
 		kvm_timer_inject_irq(vcpu);
 }

 /**
  * kvm_timer_sync_hwstate - sync timer state from cpu
  * @vcpu: The vcpu pointer
  *
  * Check if the virtual timer was armed and either schedule a corresponding
  * soft timer or inject directly if already expired.
  */
 void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 	cycle_t cval, now;
 	u64 ns;

 	BUG_ON(timer_is_armed(timer));

 	if (kvm_timer_should_fire(vcpu)) {
 		/*
 		 * Timer has already expired while we were not
 		 * looking. Inject the interrupt and carry on.
 		 */
 		kvm_timer_inject_irq(vcpu);
 		return;
 	}

 	cval = timer->cntv_cval;
 	now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;

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

 int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
 			 const struct kvm_irq_level *irq)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 	struct irq_phys_map *map;

 	/*
 	 * The vcpu timer irq number cannot be determined in
 	 * kvm_timer_vcpu_init() because it is called much before
 	 * kvm_vcpu_set_target(). To handle this, we determine
 	 * vcpu timer irq number when the vcpu is reset.
 	 */
 	timer->irq = irq;

 	/*
 	 * 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.
 	 */
 	timer->cntv_ctl = 0;

 	/*
 	 * Tell the VGIC that the virtual interrupt is tied to a
 	 * physical interrupt. We do that once per VCPU.
 	 */
 	map = kvm_vgic_map_phys_irq(vcpu, irq->irq, host_vtimer_irq);
 	if (WARN_ON(IS_ERR(map)))
 		return PTR_ERR(map);

 	timer->map = map;
 	return 0;
 }

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

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

 static void kvm_timer_init_interrupt(void *info)
 {
 	enable_percpu_irq(host_vtimer_irq, 0);
 }

 int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

 	switch (regid) {
 	case KVM_REG_ARM_TIMER_CTL:
 		timer->cntv_ctl = value;
 		break;
 	case KVM_REG_ARM_TIMER_CNT:
 		vcpu->kvm->arch.timer.cntvoff = kvm_phys_timer_read() - value;
 		break;
 	case KVM_REG_ARM_TIMER_CVAL:
 		timer->cntv_cval = value;
 		break;
 	default:
 		return -1;
 	}
 	return 0;
 }

 u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

 	switch (regid) {
 	case KVM_REG_ARM_TIMER_CTL:
 		return timer->cntv_ctl;
 	case KVM_REG_ARM_TIMER_CNT:
 		return kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
 	case KVM_REG_ARM_TIMER_CVAL:
 		return timer->cntv_cval;
 	}
 	return (u64)-1;
 }

 static int kvm_timer_cpu_notify(struct notifier_block *self,
 				unsigned long action, void *cpu)
 {
 	switch (action) {
 	case CPU_STARTING:
 	case CPU_STARTING_FROZEN:
 		kvm_timer_init_interrupt(NULL);
 		break;
 	case CPU_DYING:
 	case CPU_DYING_FROZEN:
 		disable_percpu_irq(host_vtimer_irq);
 		break;
 	}

 	return NOTIFY_OK;
 }

 static struct notifier_block kvm_timer_cpu_nb = {
 	.notifier_call = kvm_timer_cpu_notify,
 };

 static const struct of_device_id arch_timer_of_match[] = {
 	{ .compatible	= "arm,armv7-timer",	},
 	{ .compatible	= "arm,armv8-timer",	},
 	{},
 };

 int kvm_timer_hyp_init(void)
 {
 	struct device_node *np;
 	unsigned int ppi;
 	int err;

 	timecounter = arch_timer_get_timecounter();
 	if (!timecounter)
 		return -ENODEV;

 	np = of_find_matching_node(NULL, arch_timer_of_match);
 	if (!np) {
 		kvm_err("kvm_arch_timer: can't find DT node\n");
 		return -ENODEV;
 	}

 	ppi = irq_of_parse_and_map(np, 2);
 	if (!ppi) {
 		kvm_err("kvm_arch_timer: no virtual timer interrupt\n");
 		err = -EINVAL;
 		goto out;
 	}

 	err = request_percpu_irq(ppi, 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",
 			ppi, err);
 		goto out;
 	}

 	host_vtimer_irq = ppi;

 	err = __register_cpu_notifier(&kvm_timer_cpu_nb);
 	if (err) {
 		kvm_err("Cannot register timer CPU notifier\n");
 		goto out_free;
 	}

 	wqueue = create_singlethread_workqueue("kvm_arch_timer");
 	if (!wqueue) {
 		err = -ENOMEM;
 		goto out_free;
 	}

 	kvm_info("%s IRQ%d\n", np->name, ppi);
 	on_each_cpu(kvm_timer_init_interrupt, NULL, 1);

 	goto out;
 out_free:
 	free_percpu_irq(ppi, kvm_get_running_vcpus());
 out:
 	of_node_put(np);
 	return err;
 }

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

 	timer_disarm(timer);
 	if (timer->map)
 		kvm_vgic_unmap_phys_irq(vcpu, timer->map);
 }

 void kvm_timer_enable(struct kvm *kvm)
 {
 	if (kvm->arch.timer.enabled)
 		return;

 	/*
 	 * There is a potential race here between VCPUs starting for the first
 	 * time, which may be enabling the timer multiple times.  That doesn't
 	 * hurt though, because we're just setting a variable to the same
 	 * variable that it already was.  The important thing is that all
 	 * VCPUs have the enabled variable set, before entering the guest, if
 	 * the arch timers are enabled.
 	 */
 	if (timecounter && wqueue)
 		kvm->arch.timer.enabled = 1;
 }

 void kvm_timer_init(struct kvm *kvm)
 {
 	kvm->arch.timer.cntvoff = kvm_phys_timer_read();
 }
	/*
	* 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/of_irq.h>
	#include <linux/kvm.h>
	#include <linux/kvm_host.h>
	#include <linux/interrupt.h>

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

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

	static struct timecounter *timecounter;
	static struct workqueue_struct *wqueue;
	static unsigned int host_vtimer_irq;

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

	static bool timer_is_armed(struct arch_timer_cpu *timer)
	{
	return timer->armed;
	}

	/* timer_arm: as in "arm the timer", not as in ARM the company */
	static void timer_arm(struct arch_timer_cpu *timer, u64 ns)
	{
	timer->armed = true;
	hrtimer_start(&timer->timer, ktime_add_ns(ktime_get(), ns),
	HRTIMER_MODE_ABS);
	}

	static void timer_disarm(struct arch_timer_cpu *timer)
	{
	if (timer_is_armed(timer)) {
	hrtimer_cancel(&timer->timer);
	cancel_work_sync(&timer->expired);
	timer->armed = false;
	}
	}

	static void kvm_timer_inject_irq(struct kvm_vcpu *vcpu)
	{
	int ret;
	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

	kvm_vgic_set_phys_irq_active(timer->map, true);
	ret = kvm_vgic_inject_mapped_irq(vcpu->kvm, vcpu->vcpu_id,
	timer->map,
	timer->irq->level);
	WARN_ON(ret);
	}

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

	/*
	* We disable the timer in the world switch and let it be
	* handled by kvm_timer_sync_hwstate(). Getting a timer
	* interrupt at this point is a sure sign of some major
	* breakage.
	*/
	pr_warn("Unexpected interrupt %d on vcpu %p\n", irq, vcpu);
	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);
	vcpu->arch.timer_cpu.armed = false;

	/*
	* 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_kick(vcpu);
	}

	static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
	{
	struct arch_timer_cpu *timer;
	timer = container_of(hrt, struct arch_timer_cpu, timer);
	queue_work(wqueue, &timer->expired);
	return HRTIMER_NORESTART;
	}

	bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
	{
	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
	cycle_t cval, now;

	if ((timer->cntv_ctl & ARCH_TIMER_CTRL_IT_MASK) \|\|
	!(timer->cntv_ctl & ARCH_TIMER_CTRL_ENABLE) \|\|
	kvm_vgic_get_phys_irq_active(timer->map))
	return false;

	cval = timer->cntv_cval;
	now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;

	return cval <= now;
	}

	/**
	* kvm_timer_flush_hwstate - prepare to move the virt timer to the cpu
	* @vcpu: The vcpu pointer
	*
	* Disarm any pending soft timers, since the world-switch code will write the
	* virtual timer state back to the physical CPU.
	*/
	void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
	{
	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

	/*
	* We're about to run this vcpu again, so there is no need to
	* keep the background timer running, as we're about to
	* populate the CPU timer again.
	*/
	timer_disarm(timer);

	/*
	* If the timer expired while we were not scheduled, now is the time
	* to inject it.
	*/
	if (kvm_timer_should_fire(vcpu))
	kvm_timer_inject_irq(vcpu);
	}

	/**
	* kvm_timer_sync_hwstate - sync timer state from cpu
	* @vcpu: The vcpu pointer
	*
	* Check if the virtual timer was armed and either schedule a corresponding
	* soft timer or inject directly if already expired.
	*/
	void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
	{
	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
	cycle_t cval, now;
	u64 ns;

	BUG_ON(timer_is_armed(timer));

	if (kvm_timer_should_fire(vcpu)) {
	/*
	* Timer has already expired while we were not
	* looking. Inject the interrupt and carry on.
	*/
	kvm_timer_inject_irq(vcpu);
	return;
	}

	cval = timer->cntv_cval;
	now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;

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

	int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
	const struct kvm_irq_level *irq)
	{
	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
	struct irq_phys_map *map;

	/*
	* The vcpu timer irq number cannot be determined in
	* kvm_timer_vcpu_init() because it is called much before
	* kvm_vcpu_set_target(). To handle this, we determine
	* vcpu timer irq number when the vcpu is reset.
	*/
	timer->irq = irq;

	/*
	* 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.
	*/
	timer->cntv_ctl = 0;

	/*
	* Tell the VGIC that the virtual interrupt is tied to a
	* physical interrupt. We do that once per VCPU.
	*/
	map = kvm_vgic_map_phys_irq(vcpu, irq->irq, host_vtimer_irq);
	if (WARN_ON(IS_ERR(map)))
	return PTR_ERR(map);

	timer->map = map;
	return 0;
	}

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

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

	static void kvm_timer_init_interrupt(void *info)
	{
	enable_percpu_irq(host_vtimer_irq, 0);
	}

	int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
	{
	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

	switch (regid) {
	case KVM_REG_ARM_TIMER_CTL:
	timer->cntv_ctl = value;
	break;
	case KVM_REG_ARM_TIMER_CNT:
	vcpu->kvm->arch.timer.cntvoff = kvm_phys_timer_read() - value;
	break;
	case KVM_REG_ARM_TIMER_CVAL:
	timer->cntv_cval = value;
	break;
	default:
	return -1;
	}
	return 0;
	}

	u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
	{
	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;

	switch (regid) {
	case KVM_REG_ARM_TIMER_CTL:
	return timer->cntv_ctl;
	case KVM_REG_ARM_TIMER_CNT:
	return kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
	case KVM_REG_ARM_TIMER_CVAL:
	return timer->cntv_cval;
	}
	return (u64)-1;
	}

	static int kvm_timer_cpu_notify(struct notifier_block *self,
	unsigned long action, void *cpu)
	{
	switch (action) {
	case CPU_STARTING:
	case CPU_STARTING_FROZEN:
	kvm_timer_init_interrupt(NULL);
	break;
	case CPU_DYING:
	case CPU_DYING_FROZEN:
	disable_percpu_irq(host_vtimer_irq);
	break;
	}

	return NOTIFY_OK;
	}

	static struct notifier_block kvm_timer_cpu_nb = {
	.notifier_call = kvm_timer_cpu_notify,
	};

	static const struct of_device_id arch_timer_of_match[] = {
	{ .compatible = "arm,armv7-timer", },
	{ .compatible = "arm,armv8-timer", },
	{},
	};

	int kvm_timer_hyp_init(void)
	{
	struct device_node *np;
	unsigned int ppi;
	int err;

	timecounter = arch_timer_get_timecounter();
	if (!timecounter)
	return -ENODEV;

	np = of_find_matching_node(NULL, arch_timer_of_match);
	if (!np) {
	kvm_err("kvm_arch_timer: can't find DT node\n");
	return -ENODEV;
	}

	ppi = irq_of_parse_and_map(np, 2);
	if (!ppi) {
	kvm_err("kvm_arch_timer: no virtual timer interrupt\n");
	err = -EINVAL;
	goto out;
	}

	err = request_percpu_irq(ppi, 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",
	ppi, err);
	goto out;
	}

	host_vtimer_irq = ppi;

	err = __register_cpu_notifier(&kvm_timer_cpu_nb);
	if (err) {
	kvm_err("Cannot register timer CPU notifier\n");
	goto out_free;
	}

	wqueue = create_singlethread_workqueue("kvm_arch_timer");
	if (!wqueue) {
	err = -ENOMEM;
	goto out_free;
	}

	kvm_info("%s IRQ%d\n", np->name, ppi);
	on_each_cpu(kvm_timer_init_interrupt, NULL, 1);

	goto out;
	out_free:
	free_percpu_irq(ppi, kvm_get_running_vcpus());
	out:
	of_node_put(np);
	return err;
	}

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

	timer_disarm(timer);
	if (timer->map)
	kvm_vgic_unmap_phys_irq(vcpu, timer->map);
	}

	void kvm_timer_enable(struct kvm *kvm)
	{
	if (kvm->arch.timer.enabled)
	return;

	/*
	* There is a potential race here between VCPUs starting for the first
	* time, which may be enabling the timer multiple times. That doesn't
	* hurt though, because we're just setting a variable to the same
	* variable that it already was. The important thing is that all
	* VCPUs have the enabled variable set, before entering the guest, if
	* the arch timers are enabled.
	*/
	if (timecounter && wqueue)
	kvm->arch.timer.enabled = 1;
	}

	void kvm_timer_init(struct kvm *kvm)
	{
	kvm->arch.timer.cntvoff = kvm_phys_timer_read();
	}