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    SubjectRe: [PATCH 09/10] x86-32: use SSE for atomic64_read/set if available
    > This is what kernel_fpu_begin/kernel_fpu_end is all about.  We
    > definitely cannot leave TS cleared without the user space CPU state
    > moved to its home location, or we have yet another complicated state to
    > worry about.

    It should be relatively simple to handle, since the current code
    doesn't really rely on the TS flag but uses TS_USEDFPU.
    It would mostly be a matter of making sure TS is restored on return to
    userspace if necessary.

    > I really feel that without a *strong* use case for this, there is
    > absolutely no point.
    For the specific 32-bit atomic64_t case, it is an improvement, but not
    necessarily significant in the big picture.
    Being able to efficiently use SSE in the kernel might however be more
    broadly useful.
    memcpy/memset/etc. (assuming SSE is the best option for these at least
    on some processors) and checksums come to mind.
    Also non-temporal SSE moves might be useful for things like memory
    compaction without clobbering caches.
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