qemu-kvm/kvm-migration-Move-yank-outside-qemu_start_incoming_migr.patch

From 4c11e06222ca5a88f48f2d47adc3a7da306bb345 Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@redhat.com>
Date: Tue, 29 Jun 2021 14:13:55 -0400
Subject: [PATCH 01/39] migration: Move yank outside
 qemu_start_incoming_migration()
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RH-Author: Leonardo Brás <leobras@redhat.com>
RH-MergeRequest: 25: migration: Move yank outside qemu_start_incoming_migration()
RH-Commit: [1/2] e5694b0ae9a55f6b147c336e86fce6f4f2163db6 (LeoBras/centos-qemu-kvm)
RH-Bugzilla: 1974683
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Peter Xu <Peter Xu <peterx@redhat.com>>

Starting from commit b5eea99ec2f5c, qmp_migrate_recover() calls unregister
before calling qemu_start_incoming_migration(). I believe it wanted to mitigate
the next call to yank_register_instance(), but I think that's wrong.

Firstly, if during recover, we should keep the yank instance there, not
"quickly removing and adding it back".

Meanwhile, calling qmp_migrate_recover() twice with b5eea99ec2f5c will directly
crash the dest qemu (right now it can't; but it'll start to work right after
the next patch) because the 1st call of qmp_migrate_recover() will unregister
permanently when the channel failed to establish, then the 2nd call of
qmp_migrate_recover() crashes at yank_unregister_instance().

This patch fixes it by moving yank ops out of qemu_start_incoming_migration()
into qmp_migrate_incoming.  For qmp_migrate_recover(), drop the unregister of
yank instance too since we keep it there during the recovery phase.

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20210629181356.217312-2-peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit cc48c587d25ff5dd7dddb4e5072de9ca8464c832)
Fixes: b5eea99e ("migration: Add yank feature", 2021-01-13)
Signed-off-by: Leonardo Bras <leobras@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 migration/migration.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 4afc6069b6..f077640df2 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -454,10 +454,6 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp)
 {
     const char *p = NULL;
 
-    if (!yank_register_instance(MIGRATION_YANK_INSTANCE, errp)) {
-        return;
-    }
-
     qapi_event_send_migration(MIGRATION_STATUS_SETUP);
     if (strstart(uri, "tcp:", &p) ||
         strstart(uri, "unix:", NULL) ||
@@ -472,7 +468,6 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp)
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_incoming_migration(p, errp);
     } else {
-        yank_unregister_instance(MIGRATION_YANK_INSTANCE);
         error_setg(errp, "unknown migration protocol: %s", uri);
     }
 }
@@ -2095,9 +2090,14 @@ void qmp_migrate_incoming(const char *uri, Error **errp)
         return;
     }
 
+    if (!yank_register_instance(MIGRATION_YANK_INSTANCE, errp)) {
+        return;
+    }
+
     qemu_start_incoming_migration(uri, &local_err);
 
     if (local_err) {
+        yank_unregister_instance(MIGRATION_YANK_INSTANCE);
         error_propagate(errp, local_err);
         return;
     }
@@ -2126,7 +2126,6 @@ void qmp_migrate_recover(const char *uri, Error **errp)
      * only re-setup the migration stream and poke existing migration
      * to continue using that newly established channel.
      */
-    yank_unregister_instance(MIGRATION_YANK_INSTANCE);
     qemu_start_incoming_migration(uri, errp);
 }
 
-- 
2.27.0