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-rw-r--r--docs/specs/vhost-user.txt63
1 files changed, 61 insertions, 2 deletions
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 4eadad1d6b..e0d71e27e6 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -115,11 +115,13 @@ the ones that do:
* 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
@@ -140,8 +142,7 @@ 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:
-#define VHOST_USER_PROTOCOL_F_MQ 0
+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
@@ -152,6 +153,49 @@ 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.
+
+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 features.
+
+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 may be computed by using all the known guest
+addresses. 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
+
+Use atomic operations, as the log may be concurrently manipulated.
+
+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, VHOST_USER_RESET_OWNER message
+will be sent by the source. No further update must be done before the
+destination takes over with new regions & rings.
+
+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
-------------
@@ -236,6 +280,7 @@ Message types
Id: 6
Equivalent ioctl: VHOST_SET_LOG_BASE
Master payload: u64
+ Slave payload: N/A
Sets the logging base address.
@@ -337,3 +382,17 @@ Message types
Master payload: vring state description
Signal slave to enable or disable corresponding vring.
+
+ * 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.