KVM: x86: Warning APICv inconsistency only when vcpu APIC mode is valid

When launching a VM with x2APIC and specify more than 255 vCPUs,
the guest kernel can disable x2APIC (e.g. specify nox2apic kernel option).
The VM fallbacks to xAPIC mode, and disable the vCPU ID 255 and greater.

In this case, APICV is deactivated for the disabled vCPUs.
However, the current APICv consistency warning does not account for
this case, which results in a warning.

Therefore, modify warning logic to report only when vCPU APIC mode
is valid.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Message-Id: <20220519102709.24125-15-suravee.suthikulpanit@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 47981e97d686dea74291dd7712b53b6a1ab8c432..acd7ce1dcb9f37c3ab53388d963105e98d5160e9 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10477,7 +10477,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
                 * per-VM state, and responsing vCPUs must wait for the update
                 * to complete before servicing KVM_REQ_APICV_UPDATE.
                 */
-               WARN_ON_ONCE(kvm_vcpu_apicv_activated(vcpu) != kvm_vcpu_apicv_active(vcpu));
+               WARN_ON_ONCE((kvm_vcpu_apicv_activated(vcpu) != kvm_vcpu_apicv_active(vcpu)) &&
+                            (kvm_get_apic_mode(vcpu) != LAPIC_MODE_DISABLED));
 
                exit_fastpath = static_call(kvm_x86_vcpu_run)(vcpu);
                if (likely(exit_fastpath != EXIT_FASTPATH_REENTER_GUEST))