• Roland Dreier's avatar
    IB/uverbs: Export ib_umem_get()/ib_umem_release() to modules · f7c6a7b5
    Roland Dreier authored
    Export ib_umem_get()/ib_umem_release() and put low-level drivers in
    control of when to call ib_umem_get() to pin and DMA map userspace,
    rather than always calling it in ib_uverbs_reg_mr() before calling the
    low-level driver's reg_user_mr method.
    
    Also move these functions to be in the ib_core module instead of
    ib_uverbs, so that driver modules using them do not depend on
    ib_uverbs.
    
    This has a number of advantages:
     - It is better design from the standpoint of making generic code a
       library that can be used or overridden by device-specific code as
       the details of specific devices dictate.
     - Drivers that do not need to pin userspace memory regions do not
       need to take the performance hit of calling ib_mem_get().  For
       example, although I have not tried to implement it in this patch,
       the ipath driver should be able to avoid pinning memory and just
       use copy_{to,from}_user() to access userspace memory regions.
     - Buffers that need special mapping treatment can be identified by
       the low-level driver.  For example, it may be possible to solve
       some Altix-specific memory ordering issues with mthca CQs in
       userspace by mapping CQ buffers with extra flags.
     - Drivers that need to pin and DMA map userspace memory for things
       other than memory regions can use ib_umem_get() directly, instead
       of hacks using extra parameters to their reg_phys_mr method.  For
       example, the mlx4 driver that is pending being merged needs to pin
       and DMA map QP and CQ buffers, but it does not need to create a
       memory key for these buffers.  So the cleanest solution is for mlx4
       to call ib_umem_get() in the create_qp and create_cq methods.
    Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
    f7c6a7b5
Makefile 790 Bytes