linux-kernel - Re: [PATCH v8 22/26] KVM: VMX: Set up interception for CET MSRs

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Message-ID: <26258c1a-2908-4931-8d6f-fac6754ca2e8@intel.com>
Date: Wed, 17 Jan 2024 09:58:40 +0800
From: "Yang, Weijiang" <weijiang.yang@...el.com>
To: Yuan Yao <yuan.yao@...ux.intel.com>
CC: "seanjc@...gle.com" <seanjc@...gle.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "Hansen, Dave" <dave.hansen@...el.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "peterz@...radead.org"
	<peterz@...radead.org>, "Gao, Chao" <chao.gao@...el.com>, "Edgecombe, Rick P"
	<rick.p.edgecombe@...el.com>, "mlevitsk@...hat.com" <mlevitsk@...hat.com>,
	"john.allen@....com" <john.allen@....com>
Subject: Re: [PATCH v8 22/26] KVM: VMX: Set up interception for CET MSRs

On 1/17/2024 9:41 AM, Yang, Weijiang wrote:
> On 1/15/2024 5:58 PM, Yuan Yao wrote:
>> On Thu, Dec 21, 2023 at 09:02:35AM -0500, Yang Weijiang wrote:
[...]
>> Looks this leading to MSR_IA32_INT_SSP_TAB not intercepted
>> after below steps:
>>
>> Step 1. User space set cpuid w/  X86_FEATURE_LM, w/  SHSTK.
>> Step 2. User space set cpuid w/o X86_FEATURE_LM, w/o SHSTK.
>>
>> Then MSR_IA32_INT_SSP_TAB won't be intercepted even w/o SHSTK
>> on guest cpuid, will this lead to inconsistency when do
>> rdmsr(MSR_IA32_INT_SSP_TAB) from guest in this scenario ?
> Yes, theoretically it's possible, how about changing it as below?
>
> vmx_set_intercept_for_msr(vcpu, MSR_IA32_INT_SSP_TAB,
> 			  MSR_TYPE_RW,
> 			  incpt | !guest_cpuid_has(vcpu, X86_FEATURE_LM));
>
Oops, should be : incpt || !guest_cpuid_has(vcpu, X86_FEATURE_LM)