From 90d326f60706a990db3ed49ba338d911471578c0 Mon Sep 17 00:00:00 2001
Message-Id: <90d326f60706a990db3ed49ba338d911471578c0@dist-git>
From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <eperezma@redhat.com>
Date: Thu, 21 Jul 2022 19:29:10 +0200
Subject: [PATCH] qemu: new function to retrieve migration blocker reasons from
 QEMU
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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, or other conditions, that would cause migration to fail.

This patch adds a function that sends this query via a QMP command and
returns the resulting array of reasons. qemuMigrationSrcIsAllowed()
will be able to use the new function to ask QEMU for migration
blockers, instead of the hardcoded guesses that libvirt currently has.

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 7e52c4839fabac2d19c6f22c99142e992e3d898e)
Resolves: https://bugzilla.redhat.com/2092833
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 src/qemu/qemu_monitor.c      | 12 ++++++++++
 src/qemu/qemu_monitor.h      |  4 ++++
 src/qemu/qemu_monitor_json.c | 46 ++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_monitor_json.h |  3 +++
 4 files changed, 65 insertions(+)

diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index fda5d2f368..865a3e69ed 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -4541,3 +4541,15 @@ qemuMonitorMigrateRecover(qemuMonitor *mon,
 
     return qemuMonitorJSONMigrateRecover(mon, uri);
 }
+
+
+int
+qemuMonitorGetMigrationBlockers(qemuMonitor *mon,
+                                char ***blockers)
+{
+    VIR_DEBUG("blockers=%p", blockers);
+
+    QEMU_CHECK_MONITOR(mon);
+
+    return qemuMonitorJSONGetMigrationBlockers(mon, blockers);
+}
diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
index 95267ec6c7..0c3f023419 100644
--- a/src/qemu/qemu_monitor.h
+++ b/src/qemu/qemu_monitor.h
@@ -1554,3 +1554,7 @@ qemuMonitorChangeMemoryRequestedSize(qemuMonitor *mon,
 int
 qemuMonitorMigrateRecover(qemuMonitor *mon,
                           const char *uri);
+
+int
+qemuMonitorGetMigrationBlockers(qemuMonitor *mon,
+                                char ***blockers);
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index 3aad2ab212..84f4589c42 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -3434,6 +3434,52 @@ int qemuMonitorJSONMigrate(qemuMonitor *mon,
     return 0;
 }
 
+
+/*
+ * Get the exposed migration blockers.
+ *
+ * This function assume qemu has the capability of request them.
+ *
+ * It returns a NULL terminated array on blockers if there are any, or it set
+ * it to NULL otherwise.
+ */
+int
+qemuMonitorJSONGetMigrationBlockers(qemuMonitor *mon,
+                                    char ***blockers)
+{
+    g_autoptr(virJSONValue) cmd = NULL;
+    g_autoptr(virJSONValue) reply = NULL;
+    virJSONValue *data;
+    virJSONValue *jblockers;
+    size_t i;
+
+    *blockers = NULL;
+    if (!(cmd = qemuMonitorJSONMakeCommand("query-migrate", NULL)))
+        return -1;
+
+    if (qemuMonitorJSONCommand(mon, cmd, &reply) < 0)
+        return -1;
+
+    if (qemuMonitorJSONCheckReply(cmd, reply, VIR_JSON_TYPE_OBJECT) < 0)
+        return -1;
+
+    data = virJSONValueObjectGetObject(reply, "return");
+
+    if (!(jblockers = virJSONValueObjectGetArray(data, "blocked-reasons")))
+        return 0;
+
+    *blockers = g_new0(char *, virJSONValueArraySize(jblockers) + 1);
+    for (i = 0; i < virJSONValueArraySize(jblockers); i++) {
+        virJSONValue *jblocker = virJSONValueArrayGet(jblockers, i);
+        const char *blocker = virJSONValueGetString(jblocker);
+
+        (*blockers)[i] = g_strdup(blocker);
+    }
+
+    return 0;
+}
+
+
 int qemuMonitorJSONMigrateCancel(qemuMonitor *mon)
 {
     g_autoptr(virJSONValue) cmd = qemuMonitorJSONMakeCommand("migrate_cancel", NULL);
diff --git a/src/qemu/qemu_monitor_json.h b/src/qemu/qemu_monitor_json.h
index ad3853ae69..4e7d6a1a8d 100644
--- a/src/qemu/qemu_monitor_json.h
+++ b/src/qemu/qemu_monitor_json.h
@@ -199,6 +199,9 @@ qemuMonitorJSONMigrate(qemuMonitor *mon,
                        unsigned int flags,
                        const char *uri);
 int
+qemuMonitorJSONGetMigrationBlockers(qemuMonitor *mon,
+                                    char ***blockers);
+int
 qemuMonitorJSONGetSpiceMigrationStatus(qemuMonitor *mon,
                                        bool *spice_migrated);
 
-- 
2.35.1