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    SubjectRe: [patch 134/149] x86, paravirt: Add a global synchronization point for pvclock
    On 07/14/2010 01:45 PM, Zachary Amsden wrote:
    > clts() has no memory clobber; it is used to serialize execution of
    > code within kernel_fpu_begin() / kernel_fpu_end() blocks.
    > If the code within is reordered before the clts(), we've corrupted
    > guest FPU state.

    Hm, that's awkward - you'd really need some way of specifying ordering
    with respect to the FPU state, and "memory" would only be an approximate
    proxy of that. And not a good one, since gcc wouldn't regard
    register-only fpu ops as being affected by a memory clobber.


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