From: Sean Christopherson seanjc@google.com
commit 97a71c444a147ae41c7d0ab5b3d855d7f762f3ed upstream.
Purge the "highest ISR" cache when updating APICv state on a vCPU. The cache must not be used when APICv is active as hardware may emulate EOIs (and other operations) without exiting to KVM.
This fixes a bug where KVM will effectively block IRQs in perpetuity due to the "highest ISR" never getting reset if APICv is activated on a vCPU while an IRQ is in-service. Hardware emulates the EOI and KVM never gets a chance to update its cache.
Fixes: b26a695a1d78 ("kvm: lapic: Introduce APICv update helper function") Cc: stable@vger.kernel.org Cc: Suravee Suthikulpanit suravee.suthikulpanit@amd.com Cc: Maxim Levitsky mlevitsk@redhat.com Reviewed-by: Paolo Bonzini pbonzini@redhat.com Reviewed-by: Maxim Levitsky mlevitsk@redhat.com Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20230106011306.85230-3-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/lapic.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2429,6 +2429,7 @@ void kvm_apic_update_apicv(struct kvm_vc */ apic->isr_count = count_vectors(apic->regs + APIC_ISR); } + apic->highest_isr_cache = -1; }
void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event) @@ -2484,7 +2485,6 @@ void kvm_lapic_reset(struct kvm_vcpu *vc kvm_lapic_set_reg(apic, APIC_TMR + 0x10 * i, 0); } kvm_apic_update_apicv(vcpu); - apic->highest_isr_cache = -1; update_divide_count(apic); atomic_set(&apic->lapic_timer.pending, 0);
@@ -2772,7 +2772,6 @@ int kvm_apic_set_state(struct kvm_vcpu * __start_apic_timer(apic, APIC_TMCCT); kvm_lapic_set_reg(apic, APIC_TMCCT, 0); kvm_apic_update_apicv(vcpu); - apic->highest_isr_cache = -1; if (apic->apicv_active) { static_call_cond(kvm_x86_apicv_post_state_restore)(vcpu); static_call_cond(kvm_x86_hwapic_irr_update)(vcpu, apic_find_highest_irr(apic));