[RFC PATCH 0/6] vdpa_sim: add support for user VA

[Stefano Garzarella <sgarzare@redhat.com>]

This series adds support for the use of user virtual addresses in the
vDPA simulator devices.

The main reason for this change is to lift the pinning of all guest memory.
Especially with virtio devices implemented in software.

The next step would be to generalize the code in vdpa-sim to allow the
implementation of in-kernel software devices. Similar to vhost, but using vDPA
so we can reuse the same software stack (e.g. in QEMU) for both HW and SW
devices.

For example, we have never merged vhost-blk, and lately there has been interest.
So it would be nice to do it directly with vDPA to reuse the same code in the
VMM for both HW and SW vDPA block devices.

The main problem (addressed by this series) was due to the pinning of all
guest memory, which thus prevented the overcommit of guest memory.

There are still some TODOs to be fixed, but I would like to have your feedback
on this RFC.

Thanks,
Stefano

Note: this series is based on Linux v6.1 + couple of fixes (that I needed to
run libblkio tests) already posted but not yet merged.

Tree available here: https://gitlab.com/sgarzarella/linux/-/tree/vdpa-sim-use-va

Stefano Garzarella (6):
  vdpa: add bind_mm callback
  vhost-vdpa: use bind_mm device callback
  vringh: support VA with iotlb
  vdpa_sim: make devices agnostic for work management
  vdpa_sim: use kthread worker
  vdpa_sim: add support for user VA

 drivers/vdpa/vdpa_sim/vdpa_sim.h     |   7 +-
 include/linux/vdpa.h                 |   8 +
 include/linux/vringh.h               |   5 +-
 drivers/vdpa/mlx5/core/resources.c   |   3 +-
 drivers/vdpa/mlx5/net/mlx5_vnet.c    |   2 +-
 drivers/vdpa/vdpa_sim/vdpa_sim.c     | 132 +++++++++++++-
 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c |   6 +-
 drivers/vdpa/vdpa_sim/vdpa_sim_net.c |   6 +-
 drivers/vhost/vdpa.c                 |  22 +++
 drivers/vhost/vringh.c               | 250 +++++++++++++++++++++------
 10 files changed, 370 insertions(+), 71 deletions(-)

-- 
2.38.1