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From: Paolo Bonzini <pbonzini@redhat.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>,
	Like Xu <like.xu.linux@gmail.com>,
	Jun Nakajima <jun.nakajima@intel.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: [DROP][PATCH] KVM: x86: Fix the #GP(0) and #UD conditions for XSETBV emulation
Date: Thu, 20 Jan 2022 10:49:00 +0100	[thread overview]
Message-ID: <5de5120f-e4b1-5888-58cb-b642361ea5cd@redhat.com> (raw)
In-Reply-To: <d0855fb0-4e98-1090-a230-132b08864ed3@intel.com>

On 1/20/22 10:31, Xiaoyao Li wrote:
>>
>> So while my gut feeling that #UD would not cause a vmexit was correct,
>> technically I was reading the SDM incorrectly.
> 
> SDM also states
> 
>    Certain exceptions have priority over VM exits. These include
>    invalid-opcode exception, faults based on privilege level,
>    and general-protection exceptions that are based on checking
>    I/O permission bits in the task-state segment(TSS)
> 
> in "Relative Priority of Faults and VM Exits"
> 
> So my understanding is that the architectural check always takes the 
> higher priority than VM exit.

Good point!  It's right above in 25.1.1.  I was confused by the specific 
mention of GETSEC, but the reason for the footnote is because undefined 
GETSEC leaves cause a vmexit instead of #UD, and GETSEC vmexits also 
override #GP faults based on privilege level.

Thanks,

Paolo


      reply	other threads:[~2022-01-20  9:49 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-17  7:24 [PATCH] " Like Xu
2022-01-17  8:31 ` Paolo Bonzini
2022-01-17  9:44   ` Like Xu
2022-01-17 11:18     ` Paolo Bonzini
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 [this message]

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