[PATCH v5 0/4] Virtio shared dma-buf

[Albert Esteve <aesteve@redhat.com>]

v1 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg00598.html
v2 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg04530.html
v3 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg06126.html
v4 link -> https://lists.gnu.org/archive/html/qemu-devel/2023-06/msg05174.html
v4 -> v5:
- Allow shared table to hold pointers for vhost devices, in a struct that defines the types that the table can store
- New message VHOST_USER_GET_SHARED_OBJECT to retrieve objects stored in vhost backends
- Minor additions to support the previous items (e.g. new test usecases).

This patch covers the required steps to add support for virtio cross-device resource sharing[1],
which support is already available in the kernel.

The main usecase will be sharing dma buffers from virtio-gpu devices (as the exporter
-see VIRTIO_GPU_CMD_RESOURCE_ASSIGN_UUID in [2]), to virtio-video (under discussion)
devices (as the buffer-user or importer). Therefore, even though virtio specs talk about
resources or objects[3], this patch adds the infrastructure with dma-bufs in mind.
Note that virtio specs let the devices themselves define what a vitio object is.

These are the main parts that are covered in the patch:

- Add hash function to uuid module
- Shared resources table, to hold all resources that can be shared in the host and their assigned UUID,
  or pointers to the backend holding the resource
- Internal shared table API for virtio devices to add, lookup and remove resources
- Unit test to verify the API
- New messages to the vhost-user protocol to allow backend to interact with the shared
  table API through the control socket
- New vhost-user feature bit to enable shared objects feature

Applies cleanly to 38a6de80b917b2a822cff0e38d83563ab401c890

[1] - https://lwn.net/Articles/828988/
[2] - https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-3730006
[3] - https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-10500011

Albert Esteve (4):
  uuid: add a hash function
  virtio-dmabuf: introduce virtio-dmabuf
  vhost-user: add shared_object msg
  vhost-user: refactor send_resp code

 MAINTAINERS                               |   7 +
 docs/interop/vhost-user.rst               |  57 +++++++
 hw/display/meson.build                    |   1 +
 hw/display/virtio-dmabuf.c                | 136 +++++++++++++++++
 hw/virtio/vhost-user.c                    | 174 ++++++++++++++++++++--
 include/hw/virtio/vhost-backend.h         |   3 +
 include/hw/virtio/virtio-dmabuf.h         | 103 +++++++++++++
 include/qemu/uuid.h                       |   2 +
 subprojects/libvhost-user/libvhost-user.c | 118 +++++++++++++++
 subprojects/libvhost-user/libvhost-user.h |  55 ++++++-
 tests/unit/meson.build                    |   1 +
 tests/unit/test-uuid.c                    |  27 ++++
 tests/unit/test-virtio-dmabuf.c           | 137 +++++++++++++++++
 util/uuid.c                               |  14 ++
 14 files changed, 821 insertions(+), 14 deletions(-)
 create mode 100644 hw/display/virtio-dmabuf.c
 create mode 100644 include/hw/virtio/virtio-dmabuf.h
 create mode 100644 tests/unit/test-virtio-dmabuf.c

-- 
2.40.0