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Date:   Tue, 8 Aug 2023 23:26:30 +0800
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Subject: Re: [PATCH v5 08/19] KVM:x86: Report KVM supported CET MSRs as
 to-be-saved
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To:     Sean Christopherson <seanjc@google.com>
CC:     <pbonzini@redhat.com>, <peterz@infradead.org>,
        <john.allen@amd.com>, <kvm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <rick.p.edgecombe@intel.com>,
        <chao.gao@intel.com>, <binbin.wu@linux.intel.com>
References: <20230803042732.88515-1-weijiang.yang@intel.com>
 <20230803042732.88515-9-weijiang.yang@intel.com>
 <ZM1JmxzyMgTLeEIy@google.com>
From:   "Yang, Weijiang" <weijiang.yang@intel.com>
In-Reply-To: <ZM1JmxzyMgTLeEIy@google.com>
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On 8/5/2023 2:55 AM, Sean Christopherson wrote:
> On Thu, Aug 03, 2023, Yang Weijiang wrote:
>> Add all CET MSRs including the synthesized GUEST_SSP to report list.
>> PL{0,1,2}_SSP are independent to host XSAVE management with later
>> patches. MSR_IA32_U_CET and MSR_IA32_PL3_SSP are XSAVE-managed on
>> host side. MSR_IA32_S_CET/MSR_IA32_INT_SSP_TAB/MSR_KVM_GUEST_SSP
>> are not XSAVE-managed.
>>
>> [...]
>>   	}
>> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
>> index 82e3dafc5453..6e6292915f8c 100644
>> --- a/arch/x86/kvm/x86.h
>> +++ b/arch/x86/kvm/x86.h
>> @@ -362,6 +362,16 @@ static inline bool kvm_mpx_supported(void)
>>   		== (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR);
>>   }
>>   
>> +#define CET_XSTATE_MASK (XFEATURE_MASK_CET_USER)
> This is funky.  As of this patch, KVM reports MSR_IA32_S_CET, a supervisor MSR,
> but does not require XFEATURE_MASK_CET_KERNEL.  That eventually comes along with
> "KVM:x86: Enable guest CET supervisor xstate bit support", but as of this patch
> KVM is busted.
>
> The whole cpuid_count() code in that patch shouldn't exist, so the easiest thing
> is to just fold the KVM_SUPPORTED_XSS and CET_XSTATE_MASK changes from that patch
> into this one.
I screwed it up when tried to make it clearer :-/
Will do it, thanks!