[PATCH] KVM: x86: WARN (once) if RTC pending EOI tracking goes off the rails

[PATCH] KVM: x86: WARN (once) if RTC pending EOI tracking goes off the rails

[Sean Christopherson]

WARN once if KVM's tracking for pending EOIs for Real-Time Clock IRQs goes
off the rails, as there's no reason to bug the host or risk a DoS due to
spamming dmesg with endless WARNs.  Absolute worst case scenario, guest
time will go awry.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/ioapic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index f3f4a483ca15..34be1f0c76b3 100644
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -84,7 +84,7 @@ static void kvm_rtc_eoi_tracking_restore_all(struct kvm_ioapic *ioapic);
 
 static void rtc_status_pending_eoi_check_valid(struct kvm_ioapic *ioapic)
 {
-	if (WARN_ON(ioapic->rtc_status.pending_eoi < 0))
+	if (WARN_ON_ONCE(ioapic->rtc_status.pending_eoi < 0))
 		kvm_rtc_eoi_tracking_restore_all(ioapic);
 }
 
@@ -484,7 +484,7 @@ static int ioapic_service(struct kvm_ioapic *ioapic, int irq, bool line_status)
 		 * ensures that it is only called if it is >= zero, namely
 		 * if rtc_irq_check_coalesced returns false).
 		 */
-		BUG_ON(ioapic->rtc_status.pending_eoi != 0);
+		WARN_ON_ONCE(ioapic->rtc_status.pending_eoi);
 		ret = __kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe,
 						 &ioapic->rtc_status);
 		ioapic->rtc_status.pending_eoi = (ret < 0 ? 0 : ret);

base-commit: 9d4853b044beefa21c4ee3e18c40653601a64ced
-- 
2.55.0.rc0.738.g0c8ab3ebcc-goog

Re: [PATCH] KVM: x86: WARN (once) if RTC pending EOI tracking goes off the rails

[Huang, Kai]

On Thu, 2026-06-18 at 10:45 -0700, Sean Christopherson wrote:
> WARN once if KVM's tracking for pending EOIs for Real-Time Clock IRQs goes
> off the rails, as there's no reason to bug the host or risk a DoS due to
> spamming dmesg with endless WARNs.  Absolute worst case scenario, guest
> time will go awry.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Kai Huang <kai.huang@intel.com>

Re: [PATCH] KVM: x86: WARN (once) if RTC pending EOI tracking goes off the rails

[Paolo Bonzini]

Queued, thanks.

Paolo