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    SubjectRe: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge
    On 06/12/2012 01:56 PM, Borislav Petkov wrote:
    > On Tue, Jun 12, 2012 at 01:42:07PM -0700, H. Peter Anvin wrote:
    >> I personally don't know of any valid use case for per-core loads, and
    >> it sounds like a horrid idea.
    >
    > Vehemently agreed.
    >
    > However, last time we talked about Ingo mentioned some possibility
    > of having different microcode versions on different CPUs:
    > http://lkml.indiana.edu/hypermail/linux/kernel/1105.3/00749.html
    >
    > Hmm...
    >
    >> And yes, I would prefer a single sysfs file, or better yet a plain old
    >> device node.
    >
    > Also agreed.
    >

    There is a difference here. Mixed steppings or even mixed CPUs are,
    indeed, supported (even things like Nehalem + Westmere in the same
    system). However, the notion is that we should upload the *entire set*
    of microcodes to the kernel, and let it flash the appropriate one into
    each CPU.

    This may result in different version number on different CPUs.

    -hpa


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