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vhost-user: add shared_object msg

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Add three new vhost-user protocol
`VHOST_USER_BACKEND_SHARED_OBJECT_* messages`.
These new messages are sent from vhost-user
back-ends to interact with the virtio-dmabuf
table in order to add or remove themselves as
virtio exporters, or lookup for virtio dma-buf
shared objects.

The action taken in the front-end depends
on the type stored in the virtio shared
object hash table.

When the table holds a pointer to a vhost
backend for a given UUID, the front-end sends
a VHOST_USER_GET_SHARED_OBJECT to the
backend holding the shared object.

The messages can only be sent after successfully
negotiating a new VHOST_USER_PROTOCOL_F_SHARED_OBJECT
vhost-user protocol feature bit.

Finally, refactor code to send response message so
that all common parts both for the common REPLY_ACK
case, and other data responses, can call it and
avoid code repetition.

Signed-off-by: Albert Esteve <aesteve@redhat.com>
Message-Id: <20231002065706.94707-4-aesteve@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Albert Esteve 2023-10-02 08:57:05 +02:00 • committed by Michael S. Tsirkin
parent faefdba847
commit 1609476662
4 changed files with 216 additions and 12 deletions
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57
docs/interop/vhost-user.rst
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@ -1440,6 +1440,18 @@ Front-end message types
query the back-end for its device status as defined in the Virtio
specification.
``VHOST_USER_GET_SHARED_OBJECT``
:id: 41
:equivalent ioctl: N/A
:request payload: ``struct VhostUserShared``
:reply payload: dmabuf fd
When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
feature has been successfully negotiated, and the UUID is found
in the exporters cache, this message is submitted by the front-end
to retrieve a given dma-buf fd from a given back-end, determined by
the requested UUID. Back-end will reply passing the fd when the operation
is successful, or no fd otherwise.
Back-end message types
----------------------
@ -1528,6 +1540,51 @@ is sent by the front-end.
The state.num field is currently reserved and must be set to 0.
``VHOST_USER_BACKEND_SHARED_OBJECT_ADD``
:id: 6
:equivalent ioctl: N/A
:request payload: ``struct VhostUserShared``
:reply payload: N/A
When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
feature has been successfully negotiated, this message can be submitted
by the backends to add themselves as exporters to the virtio shared lookup
table. The back-end device gets associated with a UUID in the shared table.
The back-end is responsible of keeping its own table with exported dma-buf fds.
When another back-end tries to import the resource associated with the UUID,
it will send a message to the front-end, which will act as a proxy to the
exporter back-end. If ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, and
the back-end sets the ``VHOST_USER_NEED_REPLY`` flag, the front-end must
respond with zero when operation is successfully completed, or non-zero
otherwise.
``VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE``
:id: 7
:equivalent ioctl: N/A
:request payload: ``struct VhostUserShared``
:reply payload: N/A
When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
feature has been successfully negotiated, this message can be submitted
by the backend to remove themselves from to the virtio-dmabuf shared
table API. The shared table will remove the back-end device associated with
the UUID. If ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, and the
back-end sets the ``VHOST_USER_NEED_REPLY`` flag, the front-end must respond
with zero when operation is successfully completed, or non-zero otherwise.
``VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP``
:id: 8
:equivalent ioctl: N/A
:request payload: ``struct VhostUserShared``
:reply payload: dmabuf fd and ``u64``
When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
feature has been successfully negotiated, this message can be submitted
by the backends to retrieve a given dma-buf fd from the virtio-dmabuf
shared table given a UUID. Frontend will reply passing the fd and a zero
when the operation is successful, or non-zero otherwise. Note that if the
operation fails, no fd is sent to the backend.
.. _reply_ack:
VHOST_USER_PROTOCOL_F_REPLY_ACK