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From 51568d18bbfef1adce26d8cd33f3f4a4c12b1e78 Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Fri, 26 Jan 2018 18:53:15 +0100
Subject: [PATCH 4/4] savevm: fail if migration blockers are present

RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: <20180126185315.2342-3-dgilbert@redhat.com>
Patchwork-id: 78732
O-Subject: [RHEL7.5 qemu-kvm PATCH 2/2] savevm: fail if migration blockers are present
Bugzilla: 1536883
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

From: Greg Kurz <gkurz@linux.vnet.ibm.com>

QEMU has currently two ways to prevent migration to occur:
- migration blocker when it depends on runtime state
- VMStateDescription.unmigratable when migration is not supported at all

This patch gathers all the logic into a single function to be called from
both the savevm and the migrate paths.

This fixes a bug with 9p, at least, where savevm would succeed and the
following would happen in the guest after loadvm:

$ ls /host
ls: cannot access /host: Protocol error

With this patch:

(qemu) savevm foo
Migration is disabled when VirtFS export path '/' is mounted in the guest
using mount_tag 'host'

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <146239057139.11271.9011797645454781543.stgit@bahia.huguette.org>
[Update subject according to Paolo's suggestion - Amit]
(cherry picked from commit 24f3902b088cd4f2dbebfd90527b5d81d6a050e9)
  dgilbert: Manual merge

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 include/migration/migration.h |  1 +
 migration.c                   | 21 +++++++++++++++------
 savevm.c                      |  2 +-
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index c99a67c..0760984 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -90,6 +90,7 @@ int migrate_fd_close(MigrationState *s);
 
 void add_migration_state_change_notifier(Notifier *notify);
 void remove_migration_state_change_notifier(Notifier *notify);
+bool migration_is_blocked(Error **errp);
 bool migration_in_setup(MigrationState *);
 bool migration_has_finished(MigrationState *);
 bool migration_has_failed(MigrationState *);
diff --git a/migration.c b/migration.c
index e8c5939..5591601 100644
--- a/migration.c
+++ b/migration.c
@@ -417,6 +417,20 @@ void migrate_del_blocker(Error *reason)
     migration_blockers = g_slist_remove(migration_blockers, reason);
 }
 
+bool migration_is_blocked(Error **errp)
+{
+    if (qemu_savevm_state_blocked(errp)) {
+        return true;
+    }
+
+    if (migration_blockers) {
+        *errp = error_copy(migration_blockers->data);
+        return true;
+    }
+
+    return false;
+}
+
 void qmp_migrate(const char *uri, bool has_blk, bool blk,
                  bool has_inc, bool inc, bool has_detach, bool detach,
                  Error **errp)
@@ -447,12 +461,7 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
         return;
     }
 
-    if (qemu_savevm_state_blocked(errp)) {
-        return;
-    }
-
-    if (migration_blockers) {
-        *errp = error_copy(migration_blockers->data);
+    if (migration_is_blocked(errp)) {
         return;
     }
 
diff --git a/savevm.c b/savevm.c
index d34004e..0216df2 100644
--- a/savevm.c
+++ b/savevm.c
@@ -2207,7 +2207,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
         .shared = 0
     };
 
-    if (qemu_savevm_state_blocked(errp)) {
+    if (migration_is_blocked(errp)) {
         return -EINVAL;
     }
 
-- 
1.8.3.1