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From: Paolo Bonzini <pbonzini@redhat.com>
To: Like Xu <like.xu.linux@gmail.com>
Cc: Sean Christopherson <seanjc@google.com>,
	Jim Mattson <jmattson@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: x86: Fix the #GP(0) and #UD conditions for XSETBV emulation
Date: Mon, 17 Jan 2022 12:18:58 +0100	[thread overview]
Message-ID: <0d7ed850-8791-42b4-ef9a-bbaa8c52279e@redhat.com> (raw)
In-Reply-To: <9c655b21-640f-6ce8-61b4-c6444995091e@gmail.com>

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;
>>
>>
> 


  reply	other threads:[~2022-01-17 11:19 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-17  7:24 [PATCH] KVM: x86: Fix the #GP(0) and #UD conditions for XSETBV emulation Like Xu
2022-01-17  8:31 ` Paolo Bonzini
2022-01-17  9:44   ` Like Xu
2022-01-17 11:18     ` Paolo Bonzini [this message]
2022-01-20  7:48       ` [DROP][PATCH] " Like Xu
2022-01-20  9:17         ` Paolo Bonzini
2022-01-20  9:31           ` Xiaoyao Li
2022-01-20  9:49             ` Paolo Bonzini

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