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: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
---
arch/arm/kvm/arm.c | 13 +++++++++++--
include/kvm/arm_arch_timer.h | 10 ++++------
virt/kvm/arm/arch_timer.c | 30 ++++++++++++++++++++++--------
3 files changed, 37 insertions(+), 16 deletions(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 66f37c4..2d6d910 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -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;
}
diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index ad9db60..b3f45a5 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -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) {}
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 22fa819..1c0772b 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -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,
- timer->irq->irq,
- timer->irq->level);
+ 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();
}
--
2.1.2.330.g565301e.dirty
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