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KVM: x86: WARN if hrtimer callback for periodic APIC timer fires with period=0

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WARN and don't restart the hrtimer if KVM's callback runs with the guest's
APIC timer in periodic mode but with a period of '0', as not advancing the
hrtimer's deadline would put the CPU into an infinite loop of hrtimer
events.  Observing a period of '0' should be impossible, even when the
hrtimer is running on a different CPU than the vCPU, as KVM is supposed to
cancel the hrtimer before changing (or zeroing) the period, e.g. when
switching from periodic to one-shot.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20251113205114.1647493-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2025-11-13 12:51:11 -08:00
parent b3e5b670c9
commit 0ea9494be9
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kvm/lapic.c
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@@ -2970,7 +2970,7 @@ static enum hrtimer_restart apic_timer_fn(struct hrtimer *data)
apic_timer_expired(apic, true);
if (lapic_is_periodic(apic)) {
if (lapic_is_periodic(apic) && !WARN_ON_ONCE(!apic->lapic_timer.period)) {
advance_periodic_target_expiration(apic);
hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
return HRTIMER_RESTART;