linux-kernel - Re: [PATCH v8 09/16] x86/cpufeatures: Add synthetic Secure TSC bit

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Date: Tue, 23 Apr 2024 10:10:14 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, thomas.lendacky@....com, x86@...nel.org,
 kvm@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
 dave.hansen@...ux.intel.com, pgonda@...gle.com, seanjc@...gle.com,
 pbonzini@...hat.com
Subject: Re: [PATCH v8 09/16] x86/cpufeatures: Add synthetic Secure TSC bit

On 4/22/2024 6:55 PM, Borislav Petkov wrote:
> On Thu, Feb 15, 2024 at 05:01:21PM +0530, Nikunj A Dadhania wrote:
>> Add support for the synthetic CPUID flag which indicates that the SNP
>> guest is running with secure tsc enabled (MSR_AMD64_SEV Bit 11 -
> 
> "TSC"

Sure

> 
>> SecureTsc_Enabled) . This flag is there so that this capability in the
>> guests can be detected easily without reading MSRs every time accessors.
> 
> Why?
> 
> What's wrong with cc_platform_has(CC_ATTR_GUEST_SECURE_TSC) or so?
> 

That was the initial implementation, and there were review comments[1] to
use synthetic flag.

Regards
Nikunj

1. https://lore.kernel.org/lkml/20231106130041.gqoqszdxrmdomsxl@box.shutemov.name/