linux-kernel - Re: [PATCH v15 04/13] x86/sev: Change TSC MSR behavior for Secure TSC enabled guests

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Message-ID: <20241211190023.GGZ1nhR7YQWGysKeEW@fat_crate.local>
Date: Wed, 11 Dec 2024 20:00:23 +0100
From: Borislav Petkov <bp@...en8.de>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: "Nikunj A. Dadhania" <nikunj@....com>, 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 04/13] x86/sev: Change TSC MSR behavior for Secure
 TSC enabled guests

On Tue, Dec 10, 2024 at 08:29:31AM -0600, Tom Lendacky wrote:
> > This is changing the behavior for SEV-ES and SNP guests(non SECURE_TSC), TSC MSR
> > reads are converted to RDTSC. This is a good optimization. But just wanted to
> > bring up the subtle impact.
> 
> Right, I think it should still flow through the GHCB MSR request for
> non-Secure TSC guests.

Why?

I'm trying to think of a reason but I'm getting confused by what needs to
happen where and when... :-\

-- 
Regards/Gruss,
    Boris.

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