linux-kernel - Re: [PATCH] x86/acrn: Set X86_FEATURE_TSC_KNOWN

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Message-ID: <Y1fjMnX9UOVo2+K5@hirez.programming.kicks-ass.net>
Date:   Tue, 25 Oct 2022 15:22:58 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Fei Li <fei1.li@...el.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        dave.hansen@...el.com, gregkh@...uxfoundation.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, Yu1.Wang@...el.com,
        conghui.chen@...el.com, fengwei.yin@...el.com
Subject: Re: [PATCH] x86/acrn: Set X86_FEATURE_TSC_KNOWN_FREQ

On Tue, Oct 25, 2022 at 04:41:47PM +0800, Fei Li wrote:
> Avoiding recalibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
> This patch also removes `inline` for acrn_get_tsc_khz() since
> it doesn't make sense.

Can we have a few words on how this is supposed to work at all?

Supposedly the HV is providing host rate through this ACRN CPUID leaf?
How does it deal with systems where TSC isn't known stable?