[PATCH 3/3] KVM: arm64: Warn if accessing timer pending state outside of vcpu context

Marc Zyngier
2022-06-02T08:30:47Z

A recurrent bug in the KVM/arm64 code base consists in trying to
access the timer pending state outside of the vcpu context, which
makes zero sense (the pending state only exists when the vcpu
is loaded).

In order to avoid more embarassing crashes and catch the offenders
red-handed, add a warning to kvm_arch_timer_get_input_level() and
return the state as non-pending. This avoids taking the system down,
and still helps tracking down silly bugs.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/arch_timer.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 5290ca5db663..bb24a76b4224 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -1230,6 +1230,9 @@ bool kvm_arch_timer_get_input_level(int vintid)
struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
struct arch_timer_context *timer;

+ if (WARN(!vcpu, "No vcpu context!\n"))
+ return false;
+
if (vintid == vcpu_vtimer(vcpu)->irq.irq)
timer = vcpu_vtimer(vcpu);
else if (vintid == vcpu_ptimer(vcpu)->irq.irq)
--
2.34.1