linux-kernel - Re: [PATCH] x86/sev: Improve handling of writes to intercepted GUEST_TSC

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Message-ID: <20250714104424.GGaHTfiFxI_pf-vhRn@fat_crate.local>
Date: Mon, 14 Jul 2025 12:44:24 +0200
From: Borislav Petkov <bp@...en8.de>
To: Nikunj A Dadhania <nikunj@....com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, seanjc@...gle.com,
	tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
	thomas.lendacky@....com, santosh.shukla@....com
Subject: Re: [PATCH] x86/sev: Improve handling of writes to intercepted
 GUEST_TSC_FREQ

On Fri, Jul 11, 2025 at 09:42:00AM +0530, Nikunj A Dadhania wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> For Secure TSC enabled guests, don't panic when a guest writes to
> intercepted GUEST_TSC_FREQ MSR. Instead, ignore writes to GUEST_TSC_FREQ,
> similar to MSR_IA32_TSC, and log a warning instead.

Why?

Nothing should poke at the TSC MSR and those who do, deserve what they get.

> Only terminate the guest when reading from intercepted GUEST_TSC_FREQ MSR
> with Secure TSC enabled, as this indicates an unexpected hypervisor
> configuration.

Huh, this sounds weird.

What are we "fixing" here?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette