linux-kernel - Re: [PATCH v14 03/13] x86/sev: Add Secure TSC support for SNP guests

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Message-ID: <56ce5e7b-48c1-73b0-ae4b-05b80f10ccf7@amd.com>
Date: Tue, 29 Oct 2024 14:16:12 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Xiaoyao Li <xiaoyao.li@...el.com>, linux-kernel@...r.kernel.org,
 thomas.lendacky@....com, bp@...en8.de, x86@...nel.org, kvm@...r.kernel.org
Cc: mingo@...hat.com, tglx@...utronix.de, dave.hansen@...ux.intel.com,
 pgonda@...gle.com, seanjc@...gle.com, pbonzini@...hat.com
Subject: Re: [PATCH v14 03/13] x86/sev: Add Secure TSC support for SNP guests

On 10/29/2024 2:11 PM, Xiaoyao Li wrote:
> On 10/28/2024 1:34 PM, Nikunj A Dadhania wrote:
>> Add support for Secure TSC in SNP-enabled guests. Secure TSC allows guests
>> to securely use RDTSC/RDTSCP instructions, ensuring that the parameters
>> used cannot be altered by the hypervisor once the guest is launched.
>>
>> Secure TSC-enabled guests need to query TSC information from the AMD
>> Security Processor. This communication channel is encrypted between the AMD
>> Security Processor and the guest, with the hypervisor acting merely as a
>> conduit to deliver the guest messages to the AMD Security Processor. Each
>> message is protected with AEAD (AES-256 GCM). Use a minimal AES GCM library
>> to encrypt and decrypt SNP guest messages for communication with the PSP.
>>
>> Use mem_encrypt_init() to fetch SNP TSC information from the AMD Security
>> Processor and initialize snp_tsc_scale and snp_tsc_offset.
> 
> Why do it inside mem_encrypt_init()?

It was discussed here: https://lore.kernel.org/lkml/20240422132058.GBZiZkOqU0zFviMzoC@fat_crate.local/

Regards
Nikunj