linux-kernel - Re: [PATCH v15 09/13] tsc: Use the GUEST_TSC

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Message-ID: <a978259b-355b-4271-ad54-43bb013e5704@amd.com>
Date: Thu, 2 Jan 2025 10:40:05 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Borislav Petkov <bp@...en8.de>, thomas.lendacky@....com
Cc: linux-kernel@...r.kernel.org, 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 v15 09/13] tsc: Use the GUEST_TSC_FREQ MSR for discovering
 TSC frequency

On 1/1/2025 9:45 PM, Borislav Petkov wrote:
> On Wed, Jan 01, 2025 at 02:26:04PM +0530, Nikunj A. Dadhania wrote:
>> As kvm-clock would have set the callbacks, I need to point them to securetsc_get_tsc_khz().
>>
>> arch/x86/kernel/kvmclock.c:     x86_platform.calibrate_tsc = kvm_get_tsc_khz;
>> arch/x86/kernel/kvmclock.c:     x86_platform.calibrate_cpu = kvm_get_tsc_khz;
>>
>> For virtualized environments, I see that all of them are assigning the same functions to different function ptrs.
> 
> So just because the others do it, you should do it too without even figuring
> out *why*?

Again: As kvm-clock has over-ridden both the callbacks, SecureTSC needs to override them with its own.

Regards,
Nikunj