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Date:   Thu, 19 Jan 2023 10:29:49 +0530
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Subject: Re: [PATCH v7] x86/sev: Add SEV-SNP guest feature negotiation support
To:     Borislav Petkov <bp@alien8.de>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org,
        mingo@redhat.com, tglx@linutronix.de, dave.hansen@linux.intel.com,
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        michael.roth@amd.com, zhi.wang.linux@gmail.com,
        David Rientjes <rientjes@google.com>, stable@kernel.org
References: <20230118061943.534309-1-nikunj@amd.com>
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From:   "Nikunj A. Dadhania" <nikunj@amd.com>
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On 19/01/23 04:51, Borislav Petkov wrote:
> On Wed, Jan 18, 2023 at 11:49:43AM +0530, Nikunj A Dadhania wrote:
>> The hypervisor can enable various new features (SEV_FEATURES[1:63])
>> and start the SNP guest. Some of these features need guest side
>> implementation. If any of these features are enabled without guest
>> side implementation, the behavior of the SNP guest will be undefined.
>> The SNP guest boot may fail in a non-obvious way making it difficult
>> to debug.
>>
>> Instead of allowing the guest to continue and have it fail randomly
>> later, detect this early and fail gracefully.
>>
>> SEV_STATUS MSR indicates features which the hypervisor has enabled.
>> While booting, SNP guests should ascertain that all the enabled
>> features have guest side implementation. In case any feature is not
>> implemented in the guest, the guest terminates booting with GHCB
>> protocol Non-Automatic Exit(NAE) termination request event[1]. Populate
>> SW_EXITINFO2 with mask of unsupported features that the hypervisor
>> can easily report to the user.
>>
>> More details in AMD64 APM[2] Vol 2: 15.34.10 SEV_STATUS MSR
>>
>> [1] https://developer.amd.com/wp-content/resources/56421.pdf
>>     4.1.13 Termination Request
>>
>> [2] https://www.amd.com/system/files/TechDocs/40332.pdf
>>
>> Fixes: cbd3d4f7c4e5 ("x86/sev: Check SEV-SNP features support")
>> CC: Borislav Petkov <bp@alien8.de>
>> CC: David Rientjes <rientjes@google.com>
>> CC: Michael Roth <michael.roth@amd.com>
>> CC: Tom Lendacky <thomas.lendacky@amd.com>
>> CC: <stable@kernel.org>
>> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
>> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
> 
> Ok, did some massaging. See whether I've fat-fingered something:
> 

Thanks, looks good to me.

Regards
Nikunj