Commit 9a364857 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: SVM: Inhibit AVIC if vCPUs are aliased in logical mode 



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: 18f40c53 ("svm: Add VMEXIT handlers for AVIC")
Reviewed-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20230106011306.85230-25-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5063c41b

arch/x86/include/asm/kvm_host.h

+6 −0
Original line number Diff line number Diff line
@@ -1218,6 +1218,12 @@ enum kvm_apicv_inhibit { 
	 * AVIC is disabled because SEV doesn't support it.

	 */

	APICV_INHIBIT_REASON_SEV,



	/*

	 * 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 {

arch/x86/kvm/lapic.c

+5 −0
Original line number Diff line number Diff line
@@ -396,6 +396,11 @@ void kvm_recalculate_apic_map(struct kvm *kvm) 
	else

		kvm_clear_apicv_inhibit(kvm, APICV_INHIBIT_REASON_PHYSICAL_ID_ALIASED);



	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);

arch/x86/kvm/svm/avic.c

+2 −1
Original line number Diff line number Diff line
@@ -967,7 +967,8 @@ bool avic_check_apicv_inhibit_reasons(enum kvm_apicv_inhibit reason) 
			  BIT(APICV_INHIBIT_REASON_SEV)      |

			  BIT(APICV_INHIBIT_REASON_PHYSICAL_ID_ALIASED) |

			  BIT(APICV_INHIBIT_REASON_APIC_ID_MODIFIED) |

			  BIT(APICV_INHIBIT_REASON_APIC_BASE_MODIFIED);

			  BIT(APICV_INHIBIT_REASON_APIC_BASE_MODIFIED) |

			  BIT(APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED);



	return supported & BIT(reason);

}