linux-kernel - Re: [PATCH] KVM: SVM: Fix potential wrong physical id in avic_handle_ldr

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Date:   Thu, 17 Oct 2019 02:12:29 +0000
From:   linmiaohe <linmiaohe@...wei.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
CC:     "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mingfangsen <mingfangsen@...wei.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH] KVM: SVM: Fix potential wrong physical id in
 avic_handle_ldr_update


Vitaly Kuznetsov <vkuznets@...hat.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 ?

>>
>> @@ -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.