[libvirt PATCH v4 3/4] qemu_migration: get migration blockers before hardcoded checks

[Eugenio Pérez]

since qemu 6.0, if migration is blocked for some reason, 'query-migrate'
will return an array of error strings describing the migration blockers.
This can be used to check whether there are any devices blocking
migration, etc.

Enable qemuMigrationSrcIsAllowed to query it.

Signed-off-by: Eugenio Pérez <eperezma at redhat.com>
Reviewed-by: Jiri Denemark <jdenemar at redhat.com>
---
v4:
* Do not override qemuDomainGetMigrationBlockers error calling again
  virReportError.
* Replace ", " with "; " in blockers separators.

v3:
* Report message with a colon.
* Report all blockers instead of only the first.
---
 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 b12cb518ee..2e3044289a 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -1414,6 +1414,20 @@ qemuMigrationSrcIsAllowedHostdev(const virDomainDef *def)
     return true;
 }
 
+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:
@@ -1439,6 +1453,22 @@ qemuMigrationSrcIsAllowed(virQEMUDriver *driver,
     int nsnapshots;
     int pauseReason;
     size_t i;
+    int r;
+
+    /* Ask qemu if it have a migration blocker */
+    if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATION_BLOCKED_REASONS)) {
+        g_auto(GStrv) blockers = NULL;
+        r = qemuDomainGetMigrationBlockers(driver, vm, &blockers);
+        if (r != 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) {
-- 
2.31.1