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

Eric Auger
2022-06-02T19:40:50Z

Hi Marc,

On 6/2/22 10:30, Marc Zyngier wrote:
> 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>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
> 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)