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authorAvi Kivity <avi@redhat.com>2009-12-29 05:42:16 -0500
committerMarcelo Tosatti <mtosatti@redhat.com>2010-01-25 09:26:36 -0500
commita5d36f82c4f3e852b61fdf1fee13463c8aa91b90 (patch)
tree5d7563cd69d710cf0948e48b26ff4b0cf197a51b /arch
parentf6760aa024199cfbce564311dc4bc4d47b6fb349 (diff)
KVM: Fix race between APIC TMR and IRR
When we queue an interrupt to the local apic, we set the IRR before the TMR. The vcpu can pick up the IRR and inject the interrupt before setting the TMR, and perhaps even EOI it, causing incorrect behaviour. The race is really insignificant since it can only occur on the first interrupt (usually following interrupts will not change TMR), but it's better closed than open. Fixed by reordering setting the TMR vs IRR. Cc: stable@kernel.org Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/lapic.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 3063a0c4858b..ba8c045da782 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -373,6 +373,12 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
373 if (unlikely(!apic_enabled(apic))) 373 if (unlikely(!apic_enabled(apic)))
374 break; 374 break;
375 375
376 if (trig_mode) {
377 apic_debug("level trig mode for vector %d", vector);
378 apic_set_vector(vector, apic->regs + APIC_TMR);
379 } else
380 apic_clear_vector(vector, apic->regs + APIC_TMR);
381
376 result = !apic_test_and_set_irr(vector, apic); 382 result = !apic_test_and_set_irr(vector, apic);
377 trace_kvm_apic_accept_irq(vcpu->vcpu_id, delivery_mode, 383 trace_kvm_apic_accept_irq(vcpu->vcpu_id, delivery_mode,
378 trig_mode, vector, !result); 384 trig_mode, vector, !result);
@@ -383,11 +389,6 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
383 break; 389 break;
384 } 390 }
385 391
386 if (trig_mode) {
387 apic_debug("level trig mode for vector %d", vector);
388 apic_set_vector(vector, apic->regs + APIC_TMR);
389 } else
390 apic_clear_vector(vector, apic->regs + APIC_TMR);
391 kvm_vcpu_kick(vcpu); 392 kvm_vcpu_kick(vcpu);
392 break; 393 break;
393 394