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[Qemu-devel] [PULL 22/38] vhost-user: document migration log
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] [PULL 22/38] vhost-user: document migration log |
Date: |
Wed, 21 Oct 2015 13:27:46 +0300 |
From: Marc-André Lureau <address@hidden>
Signed-off-by: Marc-André Lureau <address@hidden>
Reviewed-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
Tested-by: Thibaut Collet <address@hidden>
---
docs/specs/vhost-user.txt | 48 +++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 46 insertions(+), 2 deletions(-)
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 4eadad1..e0292a0 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 +153,48 @@ 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
+
Message types
-------------
@@ -236,6 +279,7 @@ Message types
Id: 6
Equivalent ioctl: VHOST_SET_LOG_BASE
Master payload: u64
+ Slave payload: N/A
Sets the logging base address.
--
MST
- [Qemu-devel] [PULL 12/38] util: add linux-only memfd fallback, (continued)
- [Qemu-devel] [PULL 12/38] util: add linux-only memfd fallback, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 13/38] util: add memfd helpers, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 14/38] util: add fallback for qemu_memfd_alloc(), Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 15/38] vhost: document log resizing, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 16/38] vhost: add vhost_set_log_base op, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 10/38] linux-headers: add unistd.h, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 17/38] vhost-user: add vhost_user_requires_shm_log(), Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 18/38] vhost: alloc shareable log, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 19/38] vhost-user: send log shm fd along with log_base, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 20/38] vhost-user: add a migration blocker, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 22/38] vhost-user: document migration log,
Michael S. Tsirkin <=
- [Qemu-devel] [PULL 21/38] vhost: use a function for each call, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 23/38] net: add trace_vhost_user_event, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 24/38] vhost user: add support of live migration, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 25/38] vhost user: add rarp sending after live migration for legacy guest, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 26/38] vhost-user: use an enum helper for features mask, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 27/38] vhost: add migration block if memfd failed, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 28/38] vhost-user-test: move wait_for_fds() out, Michael S. Tsirkin, 2015/10/21
- [Qemu-devel] [PULL 29/38] vhost-user-test: remove useless static check, Michael S. Tsirkin, 2015/10/21