Commit 3989a6d0 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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



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: 67034bb9 ("KVM: SVM: Add irqchip_split() checks before enabling AVIC")
Fixes: 6c3e4422 ("svm: Add support for dynamic APICv")
Reviewed-by: default avatarNaveen N Rao (AMD) <naveen@kernel.org>
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260203190711.458413-2-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent e2ffe85b

arch/x86/kvm/svm/avic.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/svm/svm.c

+1 −1
Original line number Diff line number Diff line
@@ -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)