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[Qemu-devel] [PATCH v5 12/21] vhost-user: document migration log
From: |
marcandre . lureau |
Subject: |
[Qemu-devel] [PATCH v5 12/21] vhost-user: document migration log |
Date: |
Thu, 24 Sep 2015 18:22:12 +0200 |
From: Marc-André Lureau <address@hidden>
Signed-off-by: Marc-André Lureau <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.
--
2.4.3
- [Qemu-devel] [PATCH v5 01/21] vhost-user: unit test for new messages, (continued)
- [Qemu-devel] [PATCH v5 01/21] vhost-user: unit test for new messages, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 02/21] configure: probe for memfd, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 03/21] util: add linux-only memfd fallback, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 04/21] util: add memfd helpers, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 05/21] vhost: alloc shareable log, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 06/21] vhost: document log resizing, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 07/21] vhost: add vhost_set_log_base op, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 09/21] vhost-user: add a migration blocker, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 08/21] vhost-user: send log shm fd along with log_base, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 11/21] vhost: only use shared log if in use by backend, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 12/21] vhost-user: document migration log,
marcandre . lureau <=
- [Qemu-devel] [PATCH v5 13/21] net: add trace_vhost_user_event, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 10/21] vhost: use a function for each call, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 14/21] vhost user: add support of live migration, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 16/21] vhost-user-test: move wait_for_fds() out, marcandre . lureau, 2015/09/24
- [Qemu-devel] [PATCH v5 15/21] vhost user: add rarp sending after live migration for legacy guest, marcandre . lureau, 2015/09/24