From 9764a6c484d4f3586b0e0be33e8c53de63b11edd Mon Sep 17 00:00:00 2001
Message-Id: <9764a6c484d4f3586b0e0be33e8c53de63b11edd@dist-git>
From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <eperezma@redhat.com>
Date: Thu, 21 Jul 2022 19:29:13 +0200
Subject: [PATCH] qemu: query QEMU for migration blockers before our own
 harcoded checks
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Since QEMU 6.0, if QEMU knows that a migration would fail,
'query-migrate' will return an array of error strings describing the
migration blockers.  This can be used to check whether there are any
devices/conditions blocking migration.

This patch adds a call to this query at the top of
qemuMigrationSrcIsAllowed().

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>

(cherry picked from commit 156e99f686690855be4e45d9b8b3194191a8bc31)
Resolves: https://bugzilla.redhat.com/2092833
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 src/qemu/qemu_migration.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 2a6b7b7819..cfb7626bb0 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -1415,6 +1415,22 @@ qemuMigrationSrcIsAllowedHostdev(const virDomainDef *def)
 }
 
 
+static int
+qemuDomainGetMigrationBlockers(virQEMUDriver *driver,
+                               virDomainObj *vm,
+                               char ***blockers)
+{
+    qemuDomainObjPrivate *priv = vm->privateData;
+    int rc;
+
+    qemuDomainObjEnterMonitor(driver, vm);
+    rc = qemuMonitorGetMigrationBlockers(priv->mon, blockers);
+    qemuDomainObjExitMonitor(vm);
+
+    return rc;
+}
+
+
 /**
  * qemuMigrationSrcIsAllowed:
  * @driver: qemu driver struct
@@ -1440,6 +1456,20 @@ qemuMigrationSrcIsAllowed(virQEMUDriver *driver,
     int pauseReason;
     size_t i;
 
+    /* Ask qemu if it has a migration blocker */
+    if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATION_BLOCKED_REASONS)) {
+        g_auto(GStrv) blockers = NULL;
+        if (qemuDomainGetMigrationBlockers(driver, vm, &blockers) < 0)
+            return false;
+
+        if (blockers && blockers[0]) {
+            g_autofree char *reasons = g_strjoinv("; ", blockers);
+            virReportError(VIR_ERR_OPERATION_INVALID,
+                           _("cannot migrate domain: %s"), reasons);
+            return false;
+        }
+    }
+
     /* perform these checks only when migrating to remote hosts */
     if (remote) {
         nsnapshots = virDomainSnapshotObjListNum(vm->snapshots, NULL, 0);
-- 
2.35.1