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* [Qemu-devel] [PATCH] migration: improve documentation of postcopy-ram
@ 2018-02-07 15:41 Greg Kurz
  2018-02-07 15:47 ` Eric Blake
  2018-02-07 15:55 ` Dr. David Alan Gilbert
  0 siblings, 2 replies; 6+ messages in thread
From: Greg Kurz @ 2018-02-07 15:41 UTC (permalink / raw)
  To: qemu-devel; +Cc: Dr. David Alan Gilbert, Juan Quintela

This capability must have the same value on both source and destination,
otherwise migration fails (commit 875fcd013ab6 "migration: incoming
postcopy advise sanity checks").

Let's write it down in various places where postcopy-ram is documented.

Signed-off-by: Greg Kurz <groug@kaod.org>
---
 docs/devel/migration.rst |    4 ++--
 hmp-commands.hx          |    3 ++-
 qapi/migration.json      |   10 ++++++----
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/docs/devel/migration.rst b/docs/devel/migration.rst
index bf97080dac2f..9d1b7657f0cf 100644
--- a/docs/devel/migration.rst
+++ b/docs/devel/migration.rst
@@ -387,8 +387,8 @@ doesn't finish in a given time the switch is made to postcopy.
 Enabling postcopy
 -----------------
 
-To enable postcopy, issue this command on the monitor prior to the
-start of migration:
+To enable postcopy, issue this command on the monitor (both source and
+destination) prior to the start of migration:
 
 ``migrate_set_capability postcopy-ram on``
 
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 15620c94d3fc..d26eb4119b9d 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1041,7 +1041,8 @@ ETEXI
         .params     = "",
         .help       = "Followup to a migration command to switch the migration"
                       " to postcopy mode. The postcopy-ram capability must "
-                      "be set before the original migration command.",
+                      "be set on both source and destination before the "
+                      "original migration command .",
         .cmd        = hmp_migrate_start_postcopy,
     },
 
diff --git a/qapi/migration.json b/qapi/migration.json
index 4cd3d1315884..7f465a1902ce 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -327,8 +327,10 @@
 #          to speed up convergence of RAM migration. (since 1.6)
 #
 # @postcopy-ram: Start executing on the migration target before all of RAM has
-#          been migrated, pulling the remaining pages along as needed. NOTE: If
-#          the migration fails during postcopy the VM will fail.  (since 2.6)
+#          been migrated, pulling the remaining pages along as needed. The
+#          capacity must have the same setting on both source and target
+#          or migration will not even start. NOTE: If the migration fails during
+#          postcopy the VM will fail.  (since 2.6)
 #
 # @x-colo: If enabled, migration will never end, and the state of the VM on the
 #        primary side will be migrated continuously to the VM on secondary
@@ -742,8 +744,8 @@
 # @migrate-start-postcopy:
 #
 # Followup to a migration command to switch the migration to postcopy mode.
-# The postcopy-ram capability must be set before the original migration
-# command.
+# The postcopy-ram capability must be set on both source and destination
+# before the original migration command.
 #
 # Since: 2.5
 #

^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-02-14 10:23 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2018-02-07 15:41 [Qemu-devel] [PATCH] migration: improve documentation of postcopy-ram Greg Kurz
2018-02-07 15:47 ` Eric Blake
2018-02-07 15:55 ` Dr. David Alan Gilbert
2018-02-14  9:44   ` Greg Kurz
2018-02-14  9:45     ` Dr. David Alan Gilbert
2018-02-14  9:55       ` Greg Kurz

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