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    SubjectRe: Enabling peer to peer device transactions for PCIe devices
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    Date

    > Well, I guess there's some consensus building to do. The existing
    > options are:
    >
    > * Device DAX: which could work but the problem I see with it is that it
    > only allows one application to do these transfers. Or there would have
    > to be some user-space coordination to figure which application gets what
    > memeroy.
    About one application restriction: so it is per memory mapping? I assume
    that
    it should not be problem for one application to do transfer to the
    several devices
    simultaneously? Am I right?

    May be we should follow RDMA MR design and register memory for p2p
    transfer from user
    space?

    What about the following:

    a) Device DAX is created
    b) "Normal" (movable, etc.) allocation will be done for PCIe memory and
    CPU pointer/access will
    be requested.
    c) p2p_mr_register() will be called and CPU pointer (mmap( on DAX
    Device)) will be returned.
    Accordingly such memory will be marked as "unmovable" by e.g. graphics
    driver.
    d) When p2p is not needed then p2p_mr_unregister() will be called.

    What do you think? Will it work?


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