Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH] KVM: SVM: Fix potential wrong physical id in avic_handle_ldr_update | Date | Thu, 17 Oct 2019 11:48:48 +0200 |
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linmiaohe <linmiaohe@huawei.com> writes:
> Vitaly Kuznetsov <vkuznets@redhat.com> writes: > >>> Guest physical APIC ID may not equal to vcpu->vcpu_id in some case. >>> We may set the wrong physical id in avic_handle_ldr_update as we >>> always use vcpu->vcpu_id. > > Hi, Vitaly, thanks for your reply. > Do you think there may be a wrong physical id in > avic_handle_ldr_update too ?
Honestly I'm not sure, however, as we need to put physical id to LDR we'd rather get it from LAPIC then assume that it's == vcpu_id so I think your patch makes sense even if it fixes a theoretical issue.
But I may be missing something important about AVIC.
> >>> >>> @@ -4591,6 +4591,8 @@ static int avic_handle_ldr_update(struct kvm_vcpu *vcpu) >>> int ret = 0; >>> struct vcpu_svm *svm = to_svm(vcpu); >>> u32 ldr = kvm_lapic_get_reg(vcpu->arch.apic, APIC_LDR); >>> + u32 apic_id_reg = kvm_lapic_get_reg(vcpu->arch.apic, APIC_ID); >>> + u32 id = (apic_id_reg >> 24) & 0xff; >> >>If we reach here than we're guaranteed to be in xAPIC mode, right? Could you maybe export and use kvm_xapic_id() here then (and in >>avic_handle_apic_id_update() too)? >> > > I think we're guaranteed to be in xAPIC mode when we reach here. I would have a try to export > and use use kvm_xapic_id here and in avic_handle_apic_id_update too. > Thanks for your suggestion. > > Have a nice day. > Best wishes.
-- Vitaly
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