linux-kernel - Re: [PATCH v15 10/13] tsc: Upgrade TSC clocksource rating

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Message-ID: <20c20e60-3b55-4c57-b5a5-1a46e286e31d@amd.com>
Date: Fri, 3 Jan 2025 19:33:42 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: tglx@...utronix.de, linux-kernel@...r.kernel.org,
 thomas.lendacky@....com, x86@...nel.org, kvm@...r.kernel.org,
 mingo@...hat.com, dave.hansen@...ux.intel.com, pgonda@...gle.com,
 seanjc@...gle.com, pbonzini@...hat.com,
 Alexey Makhalov <alexey.makhalov@...adcom.com>,
 Juergen Gross <jgross@...e.com>, Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [PATCH v15 10/13] tsc: Upgrade TSC clocksource rating

On 1/3/2025 5:36 PM, Borislav Petkov wrote:
> On Fri, Jan 03, 2025 at 03:39:56PM +0530, Nikunj A. Dadhania wrote:
>> Right, let me limit this only to virtualized environments as part of 
>> CONFIG_PARAVIRT.
> 
> That's not what you do below - you check whether you're running as a guest.
> 
> And that's not sufficient as I just said. I think the only somewhat reliable
> thing you can do is when you're running as a STSC guest.

This is for all guest running with TSC that is constant, non-stop and 
stable[1] (and detailed response here [2]), STSC is one of them.

Thanks
Nikunj

1. https://lore.kernel.org/kvm/ZuR2t1QrBpPc1Sz2@google.com/
2. https://lore.kernel.org/all/8c3cc8a5-1b85-48b3-9361-523f27fb312a@amd.com/