linux-kernel - Re: [RFC PATCH v3 08/15] sched/clock, x86: Make __sched_clock

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Message-ID: <20241120145904.GK19989@noisy.programming.kicks-ass.net>
Date: Wed, 20 Nov 2024 15:59:04 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Valentin Schneider <vschneid@...hat.com>
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Subject: Re: [RFC PATCH v3 08/15] sched/clock, x86: Make __sched_clock_stable
 forceful

On Tue, Nov 19, 2024 at 04:34:55PM +0100, Valentin Schneider wrote:
> Later commits will cause objtool to warn about non __ro_after_init static
> keys being used in .noinstr sections in order to safely defer instruction
> patching IPIs targeted at NOHZ_FULL CPUs.
> 
> __sched_clock_stable is used in .noinstr code, and can be modified at
> runtime (e.g. KVM module loading). Suppressing the text_poke_sync() IPI has

Wait, what !? loading KVM causes the TSC to be marked unstable?