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charset="utf-8" Add SHMEM_MAP/_UNMAP request to the vhost-user spec documentation. Reviewed-by: Stefan Hajnoczi Reviewed-by: Manos Pitsidianakis Signed-off-by: Albert Esteve Reviewed-by: Alyssa Ross Reviewed-by: Stefano Garzarella --- docs/interop/vhost-user.rst | 61 +++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst index 17a68a62eb..ae4ad6f441 100644 --- a/docs/interop/vhost-user.rst +++ b/docs/interop/vhost-user.rst @@ -350,6 +350,27 @@ Device state transfer parameters In the future, additional phases might be added e.g. to allow iterative migration while the device is running. =20 +MMAP request +^^^^^^^^^^^^ + ++-------+---------+-----------+------------+-----+-------+ +| shmid | padding | fd_offset | shm_offset | len | flags | ++-------+---------+-----------+------------+-----+-------+ + +:shmid: a 8-bit shared memory region identifier + +:fd_offset: a 64-bit offset of this area from the start + of the supplied file descriptor + +:shm_offset: a 64-bit offset from the start of the + pointed shared memory region + +:len: a 64-bit size of the memory to map + +:flags: a 64-bit value: + - 0: Pages are mapped read-only + - 1: Pages are mapped read-write + C structure ----------- =20 @@ -375,6 +396,7 @@ In QEMU the vhost-user message is implemented with the = following struct: VhostUserInflight inflight; VhostUserShared object; VhostUserTransferDeviceState transfer_state; + VhostUserMMap mmap; }; } QEMU_PACKED VhostUserMsg; =20 @@ -1064,6 +1086,7 @@ Protocol features #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17 #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18 #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19 + #define VHOST_USER_PROTOCOL_F_SHMEM 20 =20 Front-end message types ----------------------- @@ -1872,6 +1895,44 @@ is sent by the front-end. when the operation is successful, or non-zero otherwise. Note that if the operation fails, no fd is sent to the backend. =20 +``VHOST_USER_BACKEND_SHMEM_MAP`` + :id: 9 + :equivalent ioctl: N/A + :request payload: fd and ``struct VhostUserMMap`` + :reply payload: N/A + + When the ``VHOST_USER_PROTOCOL_F_SHMEM`` protocol feature has been + successfully negotiated, this message can be submitted by the backends to + advertise a new mapping to be made in a given VIRTIO Shared Memory Regio= n. + Upon receiving the message, the front-end will mmap the given fd into the + VIRTIO Shared Memory Region with the requested ``shmid``. + If ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, and + back-end set the ``VHOST_USER_NEED_REPLY`` flag, the front-end + must respond with zero when operation is successfully completed, + or non-zero otherwise. + + Mapping over an already existing map is not allowed and requests shall f= ail. + Therefore, the memory range in the request must correspond with a valid, + free region of the VIRTIO Shared Memory Region. Also, note that mappings + consume resources and that the request can fail when there are no resour= ces + available. Lastly, mappings are automatically unmapped by the front-end + across device reset operation. + +``VHOST_USER_BACKEND_SHMEM_UNMAP`` + :id: 10 + :equivalent ioctl: N/A + :request payload: ``struct VhostUserMMap`` + :reply payload: N/A + + When the ``VHOST_USER_PROTOCOL_F_SHMEM`` protocol feature has been + successfully negotiated, this message can be submitted by the backends so + that the front-end un-mmaps a given range (``shm_offset``, ``len``) in t= he + VIRTIO Shared Memory Region with the requested ``shmid``. Note that the + given range shall correspond to the entirety of a valid mapped region. + 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. + .. _reply_ack: =20 VHOST_USER_PROTOCOL_F_REPLY_ACK --=20 2.52.0