Inhibit SVM's AVIC if multiple vCPUs are aliased to the same logical ID. Architecturally, all CPUs whose logical ID matches the MDA are supposed to receive the interrupt; overwriting existing entries in AVIC's logical=>physical map can result in missed IPIs. Fixes: 18f40c53e10f ("svm: Add VMEXIT handlers for AVIC") Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/include/asm/kvm_host.h | 6 ++++++ arch/x86/kvm/lapic.c | 5 +++++ arch/x86/kvm/svm/avic.c | 3 ++- 3 files changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 13dadc96d9ac..042dcdf987d2 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1144,6 +1144,12 @@ enum kvm_apicv_inhibit { * inhibits, this is sticky for simplicity. */ APICV_INHIBIT_REASON_X2APIC, + + /* + * AVIC is disabled because not all vCPUs with a valid LDR have a 1:1 + * mapping between logical ID and vCPU. + */ + APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED, }; struct kvm_arch { diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 407e933eb073..4cebbdd3431b 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -364,6 +364,11 @@ void kvm_recalculate_apic_map(struct kvm *kvm) cluster[ldr] = apic; } out: + if (!new || new->logical_mode == KVM_APIC_MODE_MAP_DISABLED) + kvm_set_apicv_inhibit(kvm, APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED); + else + kvm_clear_apicv_inhibit(kvm, APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED); + old = rcu_dereference_protected(kvm->arch.apic_map, lockdep_is_held(&kvm->arch.apic_map_lock)); rcu_assign_pointer(kvm->arch.apic_map, new); diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index 3400046ad0b4..efb0632d7457 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -994,7 +994,8 @@ bool avic_check_apicv_inhibit_reasons(enum kvm_apicv_inhibit reason) BIT(APICV_INHIBIT_REASON_SEV) | BIT(APICV_INHIBIT_REASON_APIC_ID_MODIFIED) | BIT(APICV_INHIBIT_REASON_APIC_BASE_MODIFIED) | - BIT(APICV_INHIBIT_REASON_X2APIC); + BIT(APICV_INHIBIT_REASON_X2APIC) | + BIT(APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED); return supported & BIT(reason); } -- 2.37.2.789.g6183377224-goog