From 03890605dc981f46ac72d17e4ac7db0da1b88e97 Mon Sep 17 00:00:00 2001
From: Jiri Denemark <jdenemar@redhat.com>
Date: Sat, 6 Sep 2014 01:16:20 +0200
Subject: [PATCH] qemu: Propagate QEMU errors during incoming migrations

When QEMU fails during incoming migration after we successfully started
it (i.e., during Perform or Finish phase), we report a rather unhelpful
message

    Unable to read from monitor: Connection reset by peer

We already have a code that takes error messages from QEMU's error
output but we disable it once QEMU successfully starts. This patch
postpones this until the end of Finish phase during incoming migration
so that we can report a much better error message:

    internal error: early end of file from monitor: possible problem:
    Unknown savevm section or instance '0000:00:05.0/virtio-balloon' 0
    load of migration failed

https://bugzilla.redhat.com/show_bug.cgi?id=1090093

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
---
 src/qemu/qemu_migration.c |  2 ++
 src/qemu/qemu_monitor.c   | 12 +++++++++---
 src/qemu/qemu_process.c   |  6 ++++--
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index f2b421eaef..64f0d8df1c 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -4689,6 +4689,8 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
  cleanup:
     virPortAllocatorRelease(driver->migrationPorts, port);
     if (vm) {
+        if (priv->mon)
+            qemuMonitorSetDomainLog(priv->mon, -1);
         VIR_FREE(priv->origname);
         virObjectUnlock(vm);
     }
diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index d96b1b80cf..702404a0ec 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -631,8 +631,11 @@ qemuMonitorIO(int watch, int fd, int events, void *opaque)
         error = true;
     } else {
         if (events & VIR_EVENT_HANDLE_WRITABLE) {
-            if (qemuMonitorIOWrite(mon) < 0)
+            if (qemuMonitorIOWrite(mon) < 0) {
                 error = true;
+                if (errno == ECONNRESET)
+                    hangup = true;
+            }
             events &= ~VIR_EVENT_HANDLE_WRITABLE;
         }
 
@@ -642,6 +645,8 @@ qemuMonitorIO(int watch, int fd, int events, void *opaque)
             events &= ~VIR_EVENT_HANDLE_READABLE;
             if (got < 0) {
                 error = true;
+                if (errno == ECONNRESET)
+                    hangup = true;
             } else if (got == 0) {
                 eof = true;
             } else {
@@ -683,8 +688,9 @@ qemuMonitorIO(int watch, int fd, int events, void *opaque)
         if (hangup) {
             /* Check if an error message from qemu is available and if so, use
              * it to overwrite the actual message. It's done only in early
-             * startup phases where the message from qemu is certainly more
-             * interesting than a "connection reset by peer" message.
+             * startup phases or during incoming migration when the message
+             * from qemu is certainly more interesting than a
+             * "connection reset by peer" message.
              */
             char *qemuMessage;
 
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 38ed3fee63..b1d8a324dd 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -4379,8 +4379,10 @@ int qemuProcessStart(virConnectPtr conn,
             goto cleanup;
     }
 
-    /* unset reporting errors from qemu log */
-    qemuMonitorSetDomainLog(priv->mon, -1);
+    /* Keep watching qemu log for errors during incoming migration, otherwise
+     * unset reporting errors from qemu log. */
+    if (!migrateFrom)
+        qemuMonitorSetDomainLog(priv->mon, -1);
 
     virCommandFree(cmd);
     VIR_FORCE_CLOSE(logfile);