[PATCH rdma-next 0/4] Add pinned revocable dmabuf import interface

[Jacob Moroni <jmoroni@google.com>]

Some dmabuf exporters (VFIO) will require that pinned importers support
revocation. In order to support this for non-ODP drivers/devices, a new
interface is required. This new interface implements a two step process
where the driver will perform a sequence like:

    ib_umem_dmabuf_get_pinned_revocable_and_lock()
    
        ... Driver MR allocation/initialization/registration/etc
        
    ib_umem_dmabuf_set_revoke_locked()
    dma_resv_unlock();
    
This allows the driver to provide a callback that can be used to
perform the actual invalidation in a way that is safe against races
from concurrent revocations during initialization.

The driver must ensure that the HW will no longer access the region
before the revoke callback returns. For MRs, this can be achieved
by using the rereg capability to set the region length to 0, or
perhaps by moving the region to a new quarantine PD. For HW that
allows the driver to manage the keys (like irdma), this can be
achieved by deregistering the region in HW but not freeing the key
until the region is truly deregistered via ibv_dereg_mr.

Changes since RFC(s):
* Break the interface into a two step process to avoid needing
  extra state in the driver.
* Move the majority of the functionality into the core.

RFC threads:
https://lore.kernel.org/linux-rdma/20260223195333.438492-1-jmoroni@google.com/T/#t
https://lore.kernel.org/linux-rdma/CAHYDg1TB1Xa+D700WrvrcQVdgZFE5f8iWp48EmQM9XjK9xJdew@mail.gmail.com/T/#t

Jacob Moroni (4):
  RDMA/umem: Add ib_umem_dmabuf_get_pinned_and_lock helper
  RDMA/umem: Move umem dmabuf revoke logic into helper function
  RDMA/umem: Add pinned revocable dmabuf import interface
  RDMA/irdma: Add support for revocable pinned dmabuf import

 drivers/infiniband/core/umem_dmabuf.c | 122 ++++++++++++++++++++++----
 drivers/infiniband/hw/irdma/main.h    |   1 +
 drivers/infiniband/hw/irdma/verbs.c   |  71 ++++++++++++++-
 include/rdma/ib_umem.h                |  20 +++++
 4 files changed, 195 insertions(+), 19 deletions(-)

-- 
2.53.0.414.gf7e9f6c205-goog