User address: a 64-bit user address
mmap offset: 64-bit offset where region starts in the mapped memory
+* Log description
+ ---------------------------
+ | log size | log offset |
+ ---------------------------
+ log size: size of area used for logging
+ log offset: offset from start of supplied file descriptor
+ where logging starts (i.e. where guest address 0 would be logged)
+
In QEMU the vhost-user message is implemented with the following struct:
typedef struct VhostUserMsg {
struct vhost_vring_state state;
struct vhost_vring_addr addr;
VhostUserMemory memory;
+ VhostUserLog log;
};
} QEMU_PACKED VhostUserMsg;
* VHOST_GET_FEATURES
* VHOST_GET_PROTOCOL_FEATURES
* VHOST_GET_VRING_BASE
+ * VHOST_SET_LOG_BASE (if VHOST_USER_PROTOCOL_F_LOG_SHMFD)
There are several messages that the master sends with file descriptors passed
in the ancillary data:
* VHOST_SET_MEM_TABLE
+ * VHOST_SET_LOG_BASE (if VHOST_USER_PROTOCOL_F_LOG_SHMFD)
* VHOST_SET_LOG_FD
* VHOST_SET_VRING_KICK
* VHOST_SET_VRING_CALL
a feature bit was dedicated for this purpose:
#define VHOST_USER_F_PROTOCOL_FEATURES 30
+Starting and stopping rings
+----------------------
+Client must only process each ring when it is both started and enabled.
+
+If VHOST_USER_F_PROTOCOL_FEATURES has not been negotiated, the ring is initialized
+in an enabled state.
+
+If VHOST_USER_F_PROTOCOL_FEATURES has been negotiated, the ring is initialized
+in a disabled state. Client must not process it until ring is enabled by
+VHOST_USER_SET_VRING_ENABLE with parameter 1, or after it has been disabled by
+VHOST_USER_SET_VRING_ENABLE with parameter 0.
+
+Each ring is initialized in a stopped state, client must not process it until
+ring is started, or after it has been stopped.
+
+Client must start ring upon receiving a kick (that is, detecting that file
+descriptor is readable) on the descriptor specified by
+VHOST_USER_SET_VRING_KICK, and stop ring upon receiving
+VHOST_USER_GET_VRING_BASE.
+
+While processing the rings (when they are started and enabled), client must
+support changing some configuration aspects on the fly.
+
+Multiple queue support
+----------------------
+
+Multiple queue is treated as a protocol extension, hence the slave has to
+implement protocol features first. The multiple queues feature is supported
+only when the protocol feature VHOST_USER_PROTOCOL_F_MQ (bit 0) is set.
+
+The max number of queues the slave supports can be queried with message
+VHOST_USER_GET_PROTOCOL_FEATURES. Master should stop when the number of
+requested queues is bigger than that.
+
+As all queues share one connection, the master uses a unique index for each
+queue in the sent message to identify a specified queue. One queue pair
+is enabled initially. More queues are enabled dynamically, by sending
+message VHOST_USER_SET_VRING_ENABLE.
+
+Migration
+---------
+
+During live migration, the master may need to track the modifications
+the slave makes to the memory mapped regions. The client should mark
+the dirty pages in a log. Once it complies to this logging, it may
+declare the VHOST_F_LOG_ALL vhost feature.
+
+To start/stop logging of data/used ring writes, server may send messages
+VHOST_USER_SET_FEATURES with VHOST_F_LOG_ALL and VHOST_USER_SET_VRING_ADDR with
+VHOST_VRING_F_LOG in ring's flags set to 1/0, respectively.
+
+All the modifications to memory pointed by vring "descriptor" should
+be marked. Modifications to "used" vring should be marked if
+VHOST_VRING_F_LOG is part of ring's flags.
+
+Dirty pages are of size:
+#define VHOST_LOG_PAGE 0x1000
+
+The log memory fd is provided in the ancillary data of
+VHOST_USER_SET_LOG_BASE message when the slave has
+VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol feature.
+
+The size of the log is supplied as part of VhostUserMsg
+which should be large enough to cover all known guest
+addresses. Log starts at the supplied offset in the
+supplied file descriptor.
+The log covers from address 0 to the maximum of guest
+regions. In pseudo-code, to mark page at "addr" as dirty:
+
+page = addr / VHOST_LOG_PAGE
+log[page / 8] |= 1 << page % 8
+
+Where addr is the guest physical address.
+
+Use atomic operations, as the log may be concurrently manipulated.
+
+Note that when logging modifications to the used ring (when VHOST_VRING_F_LOG
+is set for this ring), log_guest_addr should be used to calculate the log
+offset: the write to first byte of the used ring is logged at this offset from
+log start. Also note that this value might be outside the legal guest physical
+address range (i.e. does not have to be covered by the VhostUserMemory table),
+but the bit offset of the last byte of the ring must fall within
+the size supplied by VhostUserLog.
+
+VHOST_USER_SET_LOG_FD is an optional message with an eventfd in
+ancillary data, it may be used to inform the master that the log has
+been modified.
+
+Once the source has finished migration, rings will be stopped by
+the source. No further update must be done before rings are
+restarted.
+
+Protocol features
+-----------------
+
+#define VHOST_USER_PROTOCOL_F_MQ 0
+#define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1
+#define VHOST_USER_PROTOCOL_F_RARP 2
+
Message types
-------------
as an owner of the session. This can be used on the Slave as a
"session start" flag.
- * VHOST_USER_RESET_DEVICE
+ * VHOST_USER_RESET_OWNER
Id: 4
- Equivalent ioctl: VHOST_RESET_DEVICE
Master payload: N/A
- Issued when a new connection is about to be closed. The Master will no
- longer own this connection (and will usually close it).
+ This is no longer used. Used to be sent to request stopping
+ all rings, but some clients interpreted it to also discard
+ connection state (this interpretation would lead to bugs).
+ It is recommended that clients either ignore this message,
+ or use it to stop all rings.
* VHOST_USER_SET_MEM_TABLE
Id: 6
Equivalent ioctl: VHOST_SET_LOG_BASE
Master payload: u64
+ Slave payload: N/A
+
+ Sets logging shared memory space.
+ When slave has VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol
+ feature, the log memory fd is provided in the ancillary data of
+ VHOST_USER_SET_LOG_BASE message, the size and offset of shared
+ memory area provided in the message.
- Sets the logging base address.
* VHOST_USER_SET_LOG_FD
Query how many queues the backend supports. This request should be
sent only when VHOST_USER_PROTOCOL_F_MQ is set in quried protocol
features by VHOST_USER_GET_PROTOCOL_FEATURES.
+
+ * VHOST_USER_SET_VRING_ENABLE
+
+ Id: 18
+ Equivalent ioctl: N/A
+ Master payload: vring state description
+
+ Signal slave to enable or disable corresponding vring.
+ This request should be sent only when VHOST_USER_F_PROTOCOL_FEATURES
+ has been negotiated.
+
+ * VHOST_USER_SEND_RARP
+
+ Id: 19
+ Equivalent ioctl: N/A
+ Master payload: u64
+
+ Ask vhost user backend to broadcast a fake RARP to notify the migration
+ is terminated for guest that does not support GUEST_ANNOUNCE.
+ Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
+ VHOST_USER_GET_FEATURES and protocol feature bit VHOST_USER_PROTOCOL_F_RARP
+ is present in VHOST_USER_GET_PROTOCOL_FEATURES.
+ The first 6 bytes of the payload contain the mac address of the guest to
+ allow the vhost user backend to construct and broadcast the fake RARP.
projects / mirror_qemu.git / blobdiff