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KVM: SVM: Check vCPU ID against max x2AVIC ID if and only if x2AVIC is enabled

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When allocating the AVIC backing page, only check one of the max AVIC vs.
x2AVIC ID based on whether or not x2AVIC is enabled.  Doing so fixes a bug
where KVM incorrectly inhibits AVIC if x2AVIC is _disabled_ and any vCPU
with a non-zero APIC ID is created, as x2avic_max_physical_id is left '0'
when x2AVIC is disabled.

Fixes: 940fc47cfb ("KVM: SVM: Add AVIC support for 4k vCPUs in x2AVIC mode")
Cc: stable@vger.kernel.org
Cc: Naveen N Rao (AMD) <naveen@kernel.org>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Reviewed-by: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://patch.msgid.link/20260112232805.1512361-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-01-12 15:28:05 -08:00
parent 3611ca7c12
commit cfbe371194
1 changed files with 2 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

4
arch/x86/kvm/svm/avic.c
View file

@ -376,6 +376,7 @@ void avic_init_vmcb(struct vcpu_svm *svm, struct vmcb *vmcb)
static int avic_init_backing_page(struct kvm_vcpu *vcpu)
{
u32 max_id = x2avic_enabled ? x2avic_max_physical_id : AVIC_MAX_PHYSICAL_ID;
struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
struct vcpu_svm *svm = to_svm(vcpu);
u32 id = vcpu->vcpu_id;
@ -388,8 +389,7 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
* avic_vcpu_load() expects to be called if and only if the vCPU has
* fully initialized AVIC.
*/
if ((!x2avic_enabled && id > AVIC_MAX_PHYSICAL_ID) ||
(id > x2avic_max_physical_id)) {
if (id > max_id) {
kvm_set_apicv_inhibit(vcpu->kvm, APICV_INHIBIT_REASON_PHYSICAL_ID_TOO_BIG);
vcpu->arch.apic->apicv_active = false;
return 0;