Commit 05971120 authored by Christoffer Dall's avatar Christoffer Dall
Browse files

arm/arm64: KVM: Require in-kernel vgic for the arch timers 



It is curently possible to run a VM with architected timers support
without creating an in-kernel VGIC, which will result in interrupts from
the virtual timer going nowhere.

To address this issue, move the architected timers initialization to the
time when we run a VCPU for the first time, and then only initialize
(and enable) the architected timers if we have a properly created and
initialized in-kernel VGIC.

When injecting interrupts from the virtual timer to the vgic, the
current setup should ensure that this never calls an on-demand init of
the VGIC, which is the only call path that could return an error from
kvm_vgic_inject_irq(), so capture the return value and raise a warning
if there's an error there.

We also change the kvm_timer_init() function from returning an int to be
a void function, since the function always succeeds.

Reviewed-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
parent ca7d9c82

arch/arm/kvm/arm.c

+11 −2
Original line number Diff line number Diff line
@@ -425,6 +425,7 @@ static void update_vttbr(struct kvm *kvm) 


static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)

{

	struct kvm *kvm = vcpu->kvm;

	int ret;



	if (likely(vcpu->arch.has_run_once))
@@ -436,12 +437,20 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) 
	 * Map the VGIC hardware resources before running a vcpu the first

	 * time on this VM.

	 */

	if (unlikely(!vgic_ready(vcpu->kvm))) {

		ret = kvm_vgic_map_resources(vcpu->kvm);

	if (unlikely(!vgic_ready(kvm))) {

		ret = kvm_vgic_map_resources(kvm);

		if (ret)

			return ret;

	}



	/*

	 * Enable the arch timers only if we have an in-kernel VGIC

	 * and it has been properly initialized, since we cannot handle

	 * interrupts from the virtual timer with a userspace gic.

	 */

	if (irqchip_in_kernel(kvm) && vgic_initialized(kvm))

		kvm_timer_enable(kvm);



	return 0;

}

include/kvm/arm_arch_timer.h

+4 −6
Original line number Diff line number Diff line
@@ -60,7 +60,8 @@ struct arch_timer_cpu { 


#ifdef CONFIG_KVM_ARM_TIMER

int kvm_timer_hyp_init(void);

int kvm_timer_init(struct kvm *kvm);

void kvm_timer_enable(struct kvm *kvm);

void kvm_timer_init(struct kvm *kvm);

void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,

			  const struct kvm_irq_level *irq);

void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu);
@@ -77,11 +78,8 @@ static inline int kvm_timer_hyp_init(void) 
	return 0;

};



static inline int kvm_timer_init(struct kvm *kvm)

{

	return 0;

}



static inline void kvm_timer_enable(struct kvm *kvm) {}

static inline void kvm_timer_init(struct kvm *kvm) {}

static inline void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,

					const struct kvm_irq_level *irq) {}

static inline void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu) {}

virt/kvm/arm/arch_timer.c

+22 −8
Original line number Diff line number Diff line
@@ -61,12 +61,14 @@ static void timer_disarm(struct arch_timer_cpu *timer) 


static void kvm_timer_inject_irq(struct kvm_vcpu *vcpu)

{

	int ret;

	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;



	timer->cntv_ctl |= ARCH_TIMER_CTRL_IT_MASK;

	kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,

	ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,

				  timer->irq->irq,

				  timer->irq->level);

	WARN_ON(ret);

}



static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
@@ -307,12 +309,24 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu) 
	timer_disarm(timer);

}



int kvm_timer_init(struct kvm *kvm)

void kvm_timer_enable(struct kvm *kvm)

{

	if (timecounter && wqueue) {

		kvm->arch.timer.cntvoff = kvm_phys_timer_read();

	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;

}



	return 0;

void kvm_timer_init(struct kvm *kvm)

{

	kvm->arch.timer.cntvoff = kvm_phys_timer_read();

}

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