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

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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")
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230106011306.85230-25-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2023-01-06 01:12:57 +00:00 committed by Paolo Bonzini
parent 5063c41beb
commit 9a364857ab
3 changed files with 13 additions and 1 deletions
arch/x86
include/asm
kvm_host.h
kvm
lapic.c
svm
avic.c

6
arch/x86/include/asm/kvm_host.h

@ -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 {

5
arch/x86/kvm/lapic.c

@ -396,6 +396,11 @@ out:
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);

3
arch/x86/kvm/svm/avic.c

@ -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);
}