linux-kernel - Re: [PATCH AUTOSEL 5.1 013/219] x86/tsc: Use CPUID.0x16 to calculate missing crystal frequency

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Message-ID: <CAD8Lp47XuF26FP0XEPz6KFMg=UGDvZx5bejjF6NZ2qSRdZSR_w@mail.gmail.com>
Date:   Tue, 16 Jul 2019 10:56:59 +0800
From:   Daniel Drake <drake@...lessm.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Len Brown <len.brown@...el.com>,
        Linux Upstreaming Team <linux@...lessm.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH AUTOSEL 5.1 013/219] x86/tsc: Use CPUID.0x16 to calculate
 missing crystal frequency

Hi,

On Mon, Jul 15, 2019 at 9:38 PM Sasha Levin <sashal@...nel.org> wrote:
> From: Daniel Drake <drake@...lessm.com>
>
> [ Upstream commit 604dc9170f2435d27da5039a3efd757dceadc684 ]

In my opinion this is not stable kernel material.

It alone does not solve a particular bug. It's part of a larger effort
to decrease usage of the 8254 PIT on modern platforms, which solves a
real problem (see "x86: skip PIT initialization on modern chipsets"),
but I'd conservatively recommend just leaving these patches out of the
stable tree. The problem has existed for a while without a
particularly wide impact, and there is a somewhat documented
workaround of changing BIOS settings.

Daniel