linux-kernel - Re: [PATCH v11 0/8] KVM: SVM: Enable Secure TSC for SEV-SNP

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Message-ID: <0a2e3ae2-6459-46eb-a9a3-2cab284a49f7@amd.com>
Date: Wed, 20 Aug 2025 17:00:39 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: "Huang, Kai" <kai.huang@...el.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "seanjc@...gle.com" <seanjc@...gle.com>
CC: "thomas.lendacky@....com" <thomas.lendacky@....com>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "vaishali.thakkar@...e.com"
	<vaishali.thakkar@...e.com>, "Ketan.Chaturvedi@....com"
	<Ketan.Chaturvedi@....com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "michael.roth@....com"
	<michael.roth@....com>, "bp@...en8.de" <bp@...en8.de>, <david.kaplan@....com>
Subject: Re: [PATCH v11 0/8] KVM: SVM: Enable Secure TSC for SEV-SNP



On 8/20/2025 4:55 PM, Huang, Kai wrote:
> On Wed, 2025-08-20 at 14:18 +0530, Nikunj A. Dadhania wrote:
>>>   - Continue on with snp_launch_start() if default_tsc_khz is '0'.  AFAICT,
>>>     continuing on doesn't put the host at (any moer) risk. [Kai]
>>
>> If I hack default_tsc_khz  as '0', SNP guest kernel with SecureTSC spits out
>> couple of warnings and finally panics:
>>  
> 
> It's a surprise that the SEV_CMD_SNP_LAUNCH_START didn't fail in such
> configuration. :-)

As mentioned here[1], this is an unsupported configuration as per the SNP
Firmware ABI.

Regards,
Nikunj

1. https://lore.kernel.org/all/c3e638e9-631f-47af-b0d2-06cea949ec1e@amd.com/