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    SubjectRe: [PATCH -v2] x86, tsc: Limit CPU frequency calibration on AMD
    On Wed, Aug 25, 2010 at 03:06:53AM -0400, Borislav Petkov wrote:
    > From: "H. Peter Anvin" <hpa@zytor.com>
    > Date: Tue, Aug 24, 2010 at 06:33:07PM -0400
    >
    > > Build failure:
    > >
    > > /home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c: In
    > > function ‘amd_calibrate_cpu’:
    > > /home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:397: error:
    > > implicit declaration of function ‘avail_to_resrv_perfctr_nmi_bit’
    > > /home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:409: error:
    > > implicit declaration of function ‘reserve_perfctr_nmi’
    > > /home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:410: error:
    > > implicit declaration of function ‘reserve_evntsel_nmi’
    > > /home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:429: error:
    > > implicit declaration of function ‘release_perfctr_nmi’
    > > /home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:430: error:
    > > implicit declaration of function ‘release_evntsel_nmi’
    > >
    > > Reproducible by doing "make ARCH=i386 allnoconfig".
    >
    > Sh*t, I can't catch a break with that Kconfig dependency stuff, can I?
    >
    > This happens because perfctr-watchdog.c gets pulled in by
    > CONFIG_X86_LOCAL_APIC which is, _of course_, not selected in an
    > allnoconfig build. Fixing this would mean exporting all that perfcounter
    > reservation functionality for the allnoconfig case, which is of course
    > doable but I'm starting to question the need for recalibrating the TSC
    > at all:
    >
    > I mean, in the 99% of the cases MSRC001_0015[24] should be set by the
    > BIOS and if not then the BIOS which does that is pretty b0rked anyway.
    > So I'm thinking of removing the recalibration code and simply warning
    > the user instead, for the 1% case.
    >
    > Andreas, what do you think?

    I opt for removing the recalibration code plus keeping a FIRMWARE_WARN
    for borked BIOSes (just in case that there are any old systems with
    the wrong setting).


    Andreas

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