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    SubjectRe: [patch 5/6] mmu_notifier: Support for drivers with revers maps (f.e. for XPmem)
    On Wednesday 20 February 2008 14:12, Robin Holt wrote:
    > For XPMEM, we do not currently allow file backed
    > mapping pages from being exported so we should never reach this condition.
    > It has been an issue since day 1. We have operated with that assumption
    > for 6 years and have not had issues with that assumption. The user of
    > xpmem is MPT and it controls the communication buffers so it is reasonable
    > to expect this type of behavior.

    OK, that makes things simpler.

    So why can't you export a device from your xpmem driver, which
    can be mmap()ed to give out "anonymous" memory pages to be used
    for these communication buffers?

    I guess you may also want an "munmap/mprotect" callback, which
    we don't have in the kernel right now... but at least you could
    prototype it easily by having an ioctl to be called before
    munmapping or mprotecting (eg. the ioctl could prevent new TLB
    setup for the region, and shoot down existing ones).

    This is actually going to be much faster for you if you use any
    threaded applications, because you will be able to do all the
    shootdown round trips outside mmap_sem, and so you will be able
    to have other threads faulting and even mmap()ing / munmaping
    at the same time as the shootdown is happening.

    I guess there is some catch...

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      Last update: 2008-02-20 04:55    [W:0.020 / U:167.200 seconds]
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