Guest-Hypervisor forwards the timer interrupt to Guest-Guest, if it is
enabled, unmasked and ISTATUS bit of register CNTV_CTL_EL0 is set for a
loaded timer.
For NV2 implementation, the Host-Hypervisor is not emulating the ISTATUS
bit while forwarding the Emulated Vtimer Interrupt to Guest-Hypervisor.
This results in the drop of interrupt from Guest-Hypervisor, where as
Host Hypervisor marked it as an active interrupt and expecting Guest-Guest
to consume and acknowledge. Due to this, some of the Guest-Guest vCPUs
are stuck in Idle thread and rcu soft lockups are seen.
This issue is not seen with NV1 case since the register CNTV_CTL_EL0 read
trap handler is emulating the ISTATUS bit.
Adding code to set/emulate the ISTATUS when the emulated timers are fired.
Signed-off-by: Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kvm/arch_timer.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 27a6ec46803a..0b32d943d2d5 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -63,6 +63,7 @@ static u64 kvm_arm_timer_read(struct kvm_vcpu *vcpu,
struct arch_timer_context *timer,
enum kvm_arch_timer_regs treg);
static bool kvm_arch_timer_get_input_level(int vintid);
+static u64 read_timer_ctl(struct arch_timer_context *timer);
static struct irq_ops arch_timer_irq_ops = {
.get_input_level = kvm_arch_timer_get_input_level,
@@ -356,6 +357,8 @@ static enum hrtimer_restart kvm_hrtimer_expire(struct hrtimer *hrt)
return HRTIMER_RESTART;
}
+ /* Timer emulated, emulate ISTATUS also */
+ timer_set_ctl(ctx, read_timer_ctl(ctx));
kvm_timer_update_irq(vcpu, true, ctx);
return HRTIMER_NORESTART;
}
@@ -458,6 +461,8 @@ static void timer_emulate(struct arch_timer_context *ctx)
trace_kvm_timer_emulate(ctx, should_fire);
if (should_fire != ctx->irq.level) {
+ /* Timer emulated, emulate ISTATUS also */
+ timer_set_ctl(ctx, read_timer_ctl(ctx));
kvm_timer_update_irq(ctx->vcpu, should_fire, ctx);
return;
}
--
2.33.1
