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KVM: SVM: Initialize AVIC VMCB fields if AVIC is enabled with in-kernel APIC

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Initialize all per-vCPU AVIC control fields in the VMCB if AVIC is enabled
in KVM and the VM has an in-kernel local APIC, i.e. if it's _possible_ the
vCPU could activate AVIC at any point in its lifecycle.  Configuring the
VMCB if and only if AVIC is active "works" purely because of optimizations
in kvm_create_lapic() to speculatively set apicv_active if AVIC is enabled
*and* to defer updates until the first KVM_RUN.  In quotes because KVM
likely won't do the right thing if kvm_apicv_activated() is false, i.e. if
a vCPU is created while APICv is inhibited at the VM level for whatever
reason.  E.g. if the inhibit is *removed* before KVM_REQ_APICV_UPDATE is
handled in KVM_RUN, then __kvm_vcpu_update_apicv() will elide calls to
vendor code due to seeing "apicv_active == activate".

Cleaning up the initialization code will also allow fixing a bug where KVM
incorrectly leaves CR8 interception enabled when AVIC is activated without
creating a mess with respect to whether AVIC is activated or not.

Cc: stable@vger.kernel.org
Fixes: 67034bb9dd ("KVM: SVM: Add irqchip_split() checks before enabling AVIC")
Fixes: 6c3e4422dd ("svm: Add support for dynamic APICv")
Reviewed-by: Naveen N Rao (AMD) <naveen@kernel.org>
Reviewed-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260203190711.458413-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2026-02-03 11:07:09 -08:00 committed by Paolo Bonzini
parent e2ffe85b6d
commit 3989a6d036
2 changed files with 2 additions and 2 deletions
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2
arch/x86/kvm/svm/avic.c
View File

@ -368,7 +368,7 @@ void avic_init_vmcb(struct vcpu_svm *svm, struct vmcb *vmcb)
vmcb->control.avic_physical_id = __sme_set(__pa(kvm_svm->avic_physical_id_table));
vmcb->control.avic_vapic_bar = APIC_DEFAULT_PHYS_BASE;
if (kvm_apicv_activated(svm->vcpu.kvm))
if (kvm_vcpu_apicv_active(&svm->vcpu))
avic_activate_vmcb(svm);
else
avic_deactivate_vmcb(svm);

2
arch/x86/kvm/svm/svm.c
View File

@ -1189,7 +1189,7 @@ static void init_vmcb(struct kvm_vcpu *vcpu, bool init_event)
if (guest_cpu_cap_has(vcpu, X86_FEATURE_ERAPS))
svm->vmcb->control.erap_ctl |= ERAP_CONTROL_ALLOW_LARGER_RAP;
if (kvm_vcpu_apicv_active(vcpu))
if (enable_apicv && irqchip_in_kernel(vcpu->kvm))
avic_init_vmcb(svm, vmcb);
if (vnmi)