linux-kernel - Re: [PATCH] x86/tsc: Add debugfs entry to mark TSC as unstable after boot

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Message-ID: <20250317144028.GEZ9g0XPSkOQU7A-nO@fat_crate.local>
Date: Mon, 17 Mar 2025 15:40:28 +0100
From: Borislav Petkov <bp@...en8.de>
To: "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	mingo@...hat.com, dave.hansen@...ux.intel.com, hpa@...or.com,
	kernel@...ccoli.net, kernel-dev@...lia.com
Subject: Re: [PATCH] x86/tsc: Add debugfs entry to mark TSC as unstable after
 boot

On Wed, Feb 26, 2025 at 10:27:13AM -0300, Guilherme G. Piccoli wrote:
> Right now, we can force the TSC to be marked as unstable through

Who's "we"?

> boot parameter. There are debug / test cases though in which would

Which are those test cases?

> be preferable to simulate the clocksource watchdog behavior, i.e.,
> marking TSC as unstable during the system run. Some paths might
> change, for example: the tracing clock is auto switched to global
> if TSC is marked as unstable on boot, but it could remain local if
> TSC gets marked as unstable after tracing initialization.
> 
> Hence, the proposal here is to have a simple debugfs file that
> gets TSC marked as unstable when written.

What happens if someone marks the TSC as unstable and comes reporting to us
that her/his machine is kaputt? And we go on a wild goose chase ...

-- 
Regards/Gruss,
    Boris.

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