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    SubjectRe: [PATCH 3/4] perf, x86: check ucode before disabling PEBS on SandyBridge v3
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    On Wed, 2012-06-13 at 13:20 -0700, Andi Kleen wrote:

    > +static int check_pebs_quirks(void)
    > +{
    > + int model = cpu_data(smp_processor_id()).x86_model;
    > +
    > + /* do not have PEBS to begin with */
    > + if (!x86_pmu.pebs)
    > + return 0;
    > +
    > + /*
    > + * check ucode version for SNB, SNB-EP
    > + */
    > + if ((model == 42 && boot_cpu_data.microcode < 0x28) ||
    > + (model == 45 && boot_cpu_data.microcode < 0x618)) {

    Stephane actually wrote:

    "Ok, so to close on this, I tried the 6/6/2012 ucode update on a few
    SNB-EP systems.

    I got two answers depending on the stepping:
    C1 (stepping 6) -> 0x618
    C2 (stepping 7) -> 0x70c

    So we need to check x86_mask for stepping and adjust the value of
    snb_ucode_rev accordingly for model 45."



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