Messages in this thread | | | Date | Thu, 5 May 2022 08:38:08 +0700 | Subject | Re: [PATCH v3 08/14] KVM: SVM: Update AVIC settings when changing APIC mode | From | Suravee Suthikulpanit <> |
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Maxim,
On 5/4/22 7:19 PM, Maxim Levitsky wrote: > On Wed, 2022-05-04 at 02:31 -0500, Suravee Suthikulpanit wrote: >> Update and refresh AVIC settings when guest APIC mode is updated >> (e.g. changing between disabled, xAPIC, or x2APIC). >> >> Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@amd.com> >> --- >> arch/x86/kvm/svm/avic.c | 16 ++++++++++++++++ >> arch/x86/kvm/svm/svm.c | 1 + >> 2 files changed, 17 insertions(+) >> >> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c >> index 3ebeea19b487..d185dd8ddf17 100644 >> --- a/arch/x86/kvm/svm/avic.c >> +++ b/arch/x86/kvm/svm/avic.c >> @@ -691,6 +691,22 @@ void avic_apicv_post_state_restore(struct kvm_vcpu *vcpu) >> avic_handle_ldr_update(vcpu); >> } >> >> +void avic_set_virtual_apic_mode(struct kvm_vcpu *vcpu) >> +{ >> + struct vcpu_svm *svm = to_svm(vcpu); >> + >> + if (!lapic_in_kernel(vcpu) || (avic_mode == AVIC_MODE_NONE)) >> + return; >> + >> + if (kvm_get_apic_mode(vcpu) == LAPIC_MODE_INVALID) { >> + WARN_ONCE(true, "Invalid local APIC state (vcpu_id=%d)", vcpu->vcpu_id); >> + return; >> + } >> + >> + kvm_vcpu_update_apicv(&svm->vcpu); > Why to have this call? I think that all that is needed is only to call the > avic_refresh_apicv_exec_ctrl.
When APIC mode is updated on each vCPU, we need to check and update vcpu->arch.apicv_active accordingly, which happens in the kvm_vcpu_update_apicv()
One test case that would fail w/o the kvm_vcpu_update_apicv() is when we boot a Linux guest w/ guest kernel option _nox2apic_, which Linux forces APIC mode of vCPUs with APIC ID 255 and higher to disable. W/o this line of code, the VM would not boot w/ more than 255 vCPUs.
Regards, Suravee
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