docs/interop/vhost-user.rst

19 This protocol is aiming to complement the ``ioctl`` interface used to
56   resort, pipe. Each file descriptor will be used for receiving or
121   bits are used:
143   - Bits 16–30: Index of the entry in the *Used Ring* where the back-end
146   - Bit 31: Device (Used) Ring Wrap Counter
152 | index | flags | descriptor | used | available | log |
161 :used: a 64-bit ring address of the vring used ring
203   amount of memory at once and unmap it after it is used.
238 :log size: a 64-bit size of area used for logging
281   - 0: Vhost front-end messages used for writable fields
282   - 1: Vhost front-end messages used for live migration
530 To start/stop logging of data/used ring writes, the front-end may send
536 be marked. Modifications to "used" vring should be marked if
560 Note that when logging modifications to the used ring (when
562 be used to calculate the log offset: the write to first byte of the
563 used ring is logged at this offset from log start. Also note that this
570 ancillary data, it may be used to inform the front-end that the log has
683 * The vhost memory region guest address is not used.
753 ``VHOST_USER_SET_INFLIGHT_FD`` are used to transfer this buffer
776       /* Maintain a list for the last batch of used descriptors.
777        * Only available when batching is used for submitting */
780       /* Used to preserve the order of fetching available descriptors.
797       /* The head of list that track the last batch of used descriptors. */
800       /* Store the idx value of used ring */
803       /* Used to track the state of each descriptor in descriptor table */
819 When supplying used buffers to the driver:
821 1. Get corresponding used head-descriptor index, i
829 #. Increase the ``idx`` value of used ring by the size of the batch
833 #. Set ``used_idx`` to the ``idx`` value of used ring
838    used ring (means the inflight field of ``DescStateSplit`` entries in
842       used ring to get last batch size of ``DescStateSplit`` entries
847    #. Set ``used_idx`` to the ``idx`` value of used ring
875       /* Used to preserve the order of fetching available descriptors.
910       /* The used index of descriptor ring */
913       /* The old used index of descriptor ring */
925       /* Used to track the state of each descriptor fetched from descriptor ring */
958 When supplying used buffers to the driver:
960 1. Get corresponding used head-descriptor entry from descriptor ring,
1012 have the kick, call and error (if used) signals done via in-band
1023 to the front-end, while the latter needs to be used with the in-band
1122   as the front-end that owns of the session. This can be used on the *back-end*
1132    This is no longer used. Used to be sent to request disabling all
1209     next index in the *Used Ring* from the respective vring structure in
1231       descriptors.  For the *Used Ring*, the device only needs the next
1262   in the ancillary data. This signals that polling should be used
1266   ``VHOST_USER_VRING_KICK`` message, it may however still be used to
1276   Set the event file descriptor to signal when buffers are used. It is
1281   in the ancillary data. This signals that polling will be used
1286   used, it may however still be used to set an event file descriptor
1304   used, it may however still be used to set an event file descriptor
1433   device configuration space and also can be used for live migration
1510   get a shared buffer from back-end. The shared buffer will be used to
1532   ancillary data. The GPU protocol is used to inform the front-end of
1590   ``VHOST_USER_REM_MEM_REG`` message, this message is used to set and
1614   ``VHOST_USER_ADD_MEM_REG`` message, this message is used to set and
1797   submitted by the back-end to indicate that a buffer was used from