docs/interop/vhost-user.rst

200   areas within this region must be mapped / unmapped only when required by the
296 :size: a 64-bit size of this area
298 :offset: a 64-bit offset of this area from the start of the
310 :mmap offset: a 64-bit offset of this area from the start
424 bit was dedicated for this purpose::
431 VIRTIO devices do not advertise this feature bit and therefore VIRTIO
490 Many devices have a fixed number of virtqueues.  In this case the front-end
520 require this protocol feature.
527 the dirty pages in a log. Once it complies to this logging, it may
561 ``VHOST_VRING_F_LOG`` is set for this ring), ``log_guest_addr`` should
563 used ring is logged at this offset from log start. Also note that this
580 'userfault'-fd and registers the memory with it; this fd is then
584 back-end.  The front-end indicates support for this via the
604 state in this transfer operation so the back-end does not need to
609 To do this, the back-end state is transferred from back-end to front-end
629 end must read all of this data (until encountering the end of file) and
732 using this fd communication channel.
736 each message) to front-end via ancillary data using this fd communication
750 this problem, the back-end need to allocate an extra buffer to store this
753 ``VHOST_USER_SET_INFLIGHT_FD`` are used to transfer this buffer
754 between front-end and back-end. And the format of this buffer is described
769       /* Indicate whether this descriptor is inflight or not.
786       /* The feature flags of this region. Now it's initialized to 0. */
789       /* The version of this region. It's 1 currently.
857       /* Indicate whether this descriptor is inflight or not.
893       /* The feature flags of this region. Now it's initialized to 0. */
896       /* The version of this region. It's 1 currently.
1019 this feature unless absolutely necessary. It is also considered an
1020 error to negotiate this feature without also negotiating
1026 use case.) As it has no other way of signalling this error, the back-end
1096    support this message even before ``VHOST_USER_SET_FEATURES`` was
1113    this message even before ``VHOST_USER_SET_FEATURES`` was called.
1134    state (this interpretation would lead to bugs).  It is recommended
1135    that back-ends either ignore this message, or use it to disable all
1156    ``NEED_REPLY_MASK`` is not set in this case.  QEMU will then
1159    reception of this message may the guest start accessing the memory
1205   Sets the next index to use for descriptors in this vring:
1228       index to process in the *Available Ring*.  Note that this may
1233       value in the vring structure in memory, so this value is not
1234       covered by this message.
1265   this message isn't necessary as the ring is also started on the
1284   ``VHOST_USER_PROTOCOL_F_BACKEND_REQ`` have been negotiated this message
1302   ``VHOST_USER_PROTOCOL_F_BACKEND_REQ`` have been negotiated this message
1407   Backends that negotiated this feature should handle both
1408   endiannesses and expect this message once (per VQ) during device
1417   When ``VHOST_USER_PROTOCOL_F_CONFIG`` is negotiated, this message is
1431   When ``VHOST_USER_PROTOCOL_F_CONFIG`` is negotiated, this message is
1472   the back-end must open a userfaultfd for later use.  Note that at this
1496   When ``VHOST_USER_PROTOCOL_F_PAGEFAULT`` is supported, this message
1509   been successfully negotiated, this message is submitted by the front-end to
1521   been successfully negotiated, this message is submitted by the front-end to
1556   feature has been successfully negotiated, this message may be
1570   feature has been successfully negotiated, this message is submitted
1584   feature has been successfully negotiated, this message is submitted
1590   ``VHOST_USER_REM_MEM_REG`` message, this message is used to set and
1608   feature has been successfully negotiated, this message is submitted
1614   ``VHOST_USER_ADD_MEM_REG`` message, this message is used to set and
1632   successfully negotiated, this message is submitted by the front-end to
1643   successfully negotiated, this message is submitted by the front-end to
1655   in the exporters cache, this message is submitted by the front-end
1668   back-end) may create the channel.  The nature of this channel is not
1669   restricted or defined in this document, but whichever side creates it
1705   flag; this flag is set when there is no file descriptor returned.
1706   When this flag is not set, the front-end must use the returned file
1710   Using this function requires prior negotiation of the
1727   Using this function requires prior negotiation of the
1733 For this type of message, the request is sent by the back-end and the reply
1780   mapping this memory range to the VM as the specified queue's notify
1781   MMIO region. The back-end sends this request to tell QEMU to de-register
1796   feature has been successfully negotiated, this message may be
1798   the vring instead of signalling this using the vring's call file
1810   feature has been successfully negotiated, this message may be
1824   feature has been successfully negotiated, this message can be submitted
1842   feature has been successfully negotiated, this message can be submitted
1858   feature has been successfully negotiated, this message can be submitted
1874 With this protocol extension negotiated, the sender (QEMU) can set the
1936   When this argument is given, the back-end program is started with the