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Date:   Fri, 20 Jan 2023 21:23:48 +1100
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Subject: Re: [PATCH kernel v3 3/3] x86/sev: Do not handle #VC for DR7
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To:     "Nikunj A. Dadhania" <nikunj@amd.com>
Cc:     kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org,
        Yury Norov <yury.norov@gmail.com>,
        Venu Busireddy <venu.busireddy@oracle.com>,
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References: <20230120031047.628097-1-aik@amd.com>
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 <adc11ed3-de89-a389-e629-3c951257469c@amd.com>
From:   Alexey Kardashevskiy <aik@amd.com>
In-Reply-To: <adc11ed3-de89-a389-e629-3c951257469c@amd.com>
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On 20/1/23 16:12, Nikunj A. Dadhania wrote:
> On 20/01/23 08:40, Alexey Kardashevskiy wrote:
>> With MSR_AMD64_SEV_DEBUG_SWAP enabled, the VM should not get #VC
>> events for DR7 read/write which it rather avoided.
>>
> 
> SNP guest feature negotiation patch is part of tip now: https://lore.kernel.org/lkml/167414649850.4906.1693185384677559889.tip-bot2@tip-bot2/

Worth mentioning it is tip/x86/urgent (which does not have 
X86_FEATURE_NO_NESTED_DATA_BP), not tip/master (which has 
X86_FEATURE_NO_NESTED_DATA_BP).

> 
> MSR_AMD64_SNP_DEBUG_SWAP is already defined. As this requires guest side changes, please add MSR_AMD64_SNP_DEBUG_SWAP as part of SNP_FEATURES_PRESENT bit mask.

It is MSR_AMD64_SEV_DEBUG_SWAP (SEV, not SNP), it is an SEV-ES thing. 
Why is that feature negotiation SNP-only and not SEV?


-- 
Alexey