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    SubjectRe: [PATCH v3 00/18] x86/tsc: Clean up rdtsc helpers
    On Tue, Jun 16, 2015 at 05:35:48PM -0700, Andy Lutomirski wrote:
    > My sincere apologies for the spam. I send an unholy mixture of the
    > real patch set and an old poorly split-up patch set, and the result
    > is incomprehensible. Here's what I meant to send.
    >
    > After the some recent threads about rdtsc barriers, I remembered
    > that our RDTSC wrappers are a big mess. Let's clean it up.
    >
    > Currently we have rdtscl, rdtscll, native_read_tsc,
    > paravirt_read_tsc, and rdtsc_barrier. For people who haven't
    > noticed rdtsc_barrier and who haven't carefully read the docs,
    > there's no indication that all of the other accessors have a giant
    > ordering gotcha. The macro forms are ugly, and the paravirt
    > implementation is completely pointless.
    >
    > rdtscl is particularly awful. It reads the low bits. There are no
    > performance critical users of just the low bits anywhere in the
    > kernel.
    >
    > Clean it up. After this patch set, there are exactly three
    > functions. rdtsc_unordered() is a function that does a raw RDTSC
    > and returns a 64-bit number. rdtsc_ordered() is a function that
    > does a properly ordered RDTSC for general-purpose use.
    > barrier_before_rdtsc() is exactly what it sounds like.
    >
    > Changes from v2:
    > - Rename rdtsc_unordered to just rdtsc
    > - Get rid of rdtsc_barrier entirely instead of renaming it
    > - The KVM patch is new (see above)
    > - Added some acks

    peterz reminded me that I'm lazy actually and don't reply to each patch :)

    So, I like it, looks good, nice cleanup. It boots on my guest here - I
    haven't done any baremetal testing though. Let's give people some more
    time to look at it...

    Thanks.

    --
    Regards/Gruss,
    Boris.

    ECO tip #101: Trim your mails when you reply.
    --


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