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    SubjectRe: One (possible) x86 get_user_pages bug
    On Thu, 2011-01-27 at 16:07 +0000, Jan Beulich wrote:
    > Nick, based on your doing of the initial implementation, would
    > you be able to estimate whether disabling get_user_pages_fast()
    > altogether for Xen would be performing measurably worse than
    > adding the locks (but continuing to avoid acquiring mm->mmap_sem)
    > as suggested by Xiaowei? That's of course only if the latter is correct
    > at all, of which I haven't fully convinced myself yet.

    Adding the lock will result in deadlocks, __get_user_pages_fast() is
    used from NMI context.

    Then again, I've got no clue if Xen even has NMIs..

     \ /
      Last update: 2011-01-27 17:27    [W:0.019 / U:58.008 seconds]
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