diff options
| author | Sean Christopherson <seanjc@google.com> | 2023-01-06 01:12:56 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2023-01-13 10:45:31 -0500 |
| commit | 5063c41bebac8d18a83ac7b5d54782d73a9ab5f7 (patch) | |
| tree | ea2ba91d40500855f925a9dd00a3b172a7e42903 /arch/x86/kvm/lapic.c | |
| parent | 5b84b0291702ea84db2c9e55696cdcdd95f9cf1a (diff) | |
KVM: x86: Inhibit APICv/AVIC if the optimized physical map is disabled
Inhibit APICv/AVIC if the optimized physical map is disabled so that KVM
KVM provides consistent APIC behavior if xAPIC IDs are aliased due to
vcpu_id being truncated and the x2APIC hotplug hack isn't enabled. If
the hotplug hack is disabled, events that are emulated by KVM will follow
architectural behavior (all matching vCPUs receive events, even if the
"match" is due to truncation), whereas APICv and AVIC will deliver events
only to the first matching vCPU, i.e. the vCPU that matches without
truncation.
Note, the "extra" inhibit is needed because KVM deliberately ignores
mismatches due to truncation when applying the APIC_ID_MODIFIED inhibit
so that large VMs (>255 vCPUs) can run with APICv/AVIC.
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230106011306.85230-24-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/lapic.c')
| -rw-r--r-- | arch/x86/kvm/lapic.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index e9f258de91bd..297da684c25f 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -386,6 +386,16 @@ void kvm_recalculate_apic_map(struct kvm *kvm) cluster[ldr] = apic; } out: + /* + * The optimized map is effectively KVM's internal version of APICv, + * and all unwanted aliasing that results in disabling the optimized + * map also applies to APICv. + */ + if (!new) + kvm_set_apicv_inhibit(kvm, APICV_INHIBIT_REASON_PHYSICAL_ID_ALIASED); + else + kvm_clear_apicv_inhibit(kvm, APICV_INHIBIT_REASON_PHYSICAL_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); @@ -2158,7 +2168,8 @@ static void kvm_lapic_xapic_id_updated(struct kvm_lapic *apic) /* * Deliberately truncate the vCPU ID when detecting a modified APIC ID * to avoid false positives if the vCPU ID, i.e. x2APIC ID, is a 32-bit - * value. + * value. If the wrap/truncation results in unwanted aliasing, APICv + * will be inhibited as part of updating KVM's optimized APIC maps. */ if (kvm_xapic_id(apic) == (u8)apic->vcpu->vcpu_id) return; |