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SubjectRe: [PATCH] KVM: x86: Fix the #GP(0) and #UD conditions for XSETBV emulation
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On 1/17/22 10:44, Like Xu wrote:
>> Also, the "Fixes" tag is not really correct as the behavior was the
>> same before.  Rather, it fixes commit 02d4160fbd76 ("x86: KVM: add
>> xsetbv to the
>
> It seems the original code comes from 81dd35d42c9a ("KVM: SVM: Add
> xsetbv intercept").
> 2acf923e38 ("KVM: VMX: Enable XSAVE/XRSTOR for guest") and 92f9895c146d.
>
>> emulator", 2019-08-22).  Checking OSXSAVE is a bug in the emulator
>> path, even though it's not needed in the XSETBV vmexit case.
>
> The kvm_emulate_xsetbv() has been removed from the emulator path.
> I'm not really sure why it's not needed in the XSETBV vmexit case. More
> details ?

Nevermind, I confused AMD (where #UD is generated before checking for
exceptions) with Intel where it's unconditional.

So the bug should be there since 2acf923e38 by executing XSETBV with
CR4.XSAVE=0. If so, please include a testcase.

Paolo

>>
>> Thanks,
>>
>> Paolo
>>
>>> +    if ((is_protmode(vcpu) && static_call(kvm_x86_get_cpl)(vcpu) !=
>>> 0) ||
>>>           __kvm_set_xcr(vcpu, kvm_rcx_read(vcpu),
>>> kvm_read_edx_eax(vcpu))) {
>>>           kvm_inject_gp(vcpu, 0);
>>>           return 1;
>>
>>
>

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