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From:   Radoslaw Biernacki <biernacki@google.com>
Date:   Mon, 11 May 2020 17:39:23 +0200
Message-ID: <CAM4=RnKVBhfnHRnvZado_8h__J2eq4BaXEK7KwdPnOoMhzco5w@mail.gmail.com>
Subject: Re: [PATCH] x86/tsc: Use hard-coded crystal clock for Skylake mobile
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Paul Menzel <pmenzel@molgen.mpg.de>, x86@kernel.org,
        Ross Zwisler <zwisler@google.com>,
        Daniel Drake <drake@endlessm.com>,
        Andy Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Len Brown <len.brown@intel.com>,
        Linux Upstreaming Team <linux@endlessm.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Thorsten Leemhuis <regressions@leemhuis.info>,
        LKML <linux-kernel@vger.kernel.org>
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On Mon, May 11, 2020 at 2:34 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Radoslaw Biernacki <biernacki@google.com> writes:
> > We found that regression only on specific SKU which was used in one
> > model of ChromeBook.
> > What's interesting is that some other SKU is fine.
> >
> > The consequences of this are rather not trivial,
> > so this was considered a quickfix and temporary till we develop
> > something better.
> > In contrast to ChromeOs, I know that there is no way of finding if
> > there are in fact regressions on generic kernel in the field (this is
> > SKU dependent),
> > but we also think that this problem should be addressed in a better
> > way (if possible).
>
> Fix the BIOS to setup the CPUID/MSRs correctly?
>
> Thanks,
>
>         tglx

Yes of course, but "if possible" might mean we would not be able to
fix the BIOS.
Anyway, let me see what actually can be done.