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    SubjectRe: [PATCH v9 00/27] x86: load FPU registers on return to userland
    On Wed, 3 Apr 2019, Sebastian Andrzej Siewior wrote:

    > This is a refurbished series originally started by by Rik van Riel. The
    > goal is load the FPU registers on return to userland and not on every
    > context switch. By this optimisation we can:
    > - avoid loading the registers if the task stays in kernel and does
    > not return to userland
    > - make kernel_fpu_begin() cheaper: it only saves the registers on the
    > first invocation. The second invocation does not need save them again.
    >
    > To access the FPU registers in kernel we need:
    > - disable preemption to avoid that the scheduler switches tasks. By
    > doing so it would set TIF_NEED_FPU_LOAD and the FPU registers would be
    > not valid.
    > - disable BH because the softirq might use kernel_fpu_begin() and then
    > set TIF_NEED_FPU_LOAD instead loading the FPU registers on completion.

    So aside of that one hunk in 24/27 which is either wrong or needs some
    information in the changelog I couldn't find anything disturbing.

    With that addressed:

    Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

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