qemuDomainSetBlockIoTune: Skip monitor call for empty cdrom

Similarly to startup of the VM qemu doesn't like setting throttling for
an empty drive. Just skip it since we do the correct thing once new
media is inserted.

Resolves: https://gitlab.com/libvirt/libvirt/-/issues/117
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Tested-by: Han Han <hhan@redhat.com>

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 1283e617859a3c080101e934cb55bb208da442d0..027617deefc7d51c02ce7d640ae70b5797780c7c 100644 (file)
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -16301,16 +16301,23 @@ qemuDomainSetBlockIoTune(virDomainPtr dom,
 
 #undef CHECK_MAX
 
-        qemuDomainObjEnterMonitor(driver, vm);
-        ret = qemuMonitorSetBlockIoThrottle(priv->mon, drivealias, qdevid,
-                                            &info, supportMaxOptions,
-                                            set_fields & QEMU_BLOCK_IOTUNE_SET_GROUP_NAME,
-                                            supportMaxLengthOptions);
-        if (qemuDomainObjExitMonitor(driver, vm) < 0)
+        /* blockdev-based qemu doesn't want to set the throttling when a cdrom
+         * is empty. Skip the monitor call here since we will set the throttling
+         * once new media is inserted */
+        if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_BLOCKDEV) ||
+            !virStorageSourceIsEmpty(disk->src)) {
+
+            qemuDomainObjEnterMonitor(driver, vm);
+            ret = qemuMonitorSetBlockIoThrottle(priv->mon, drivealias, qdevid,
+                                                &info, supportMaxOptions,
+                                                set_fields & QEMU_BLOCK_IOTUNE_SET_GROUP_NAME,
+                                                supportMaxLengthOptions);
+            if (qemuDomainObjExitMonitor(driver, vm) < 0)
+                ret = -1;
+            if (ret < 0)
+                goto endjob;
             ret = -1;
-        if (ret < 0)
-            goto endjob;
-        ret = -1;
+        }
 
         virDomainDiskSetBlockIOTune(disk, &info);