qemu: support to drop disk with 'optional' startupPolicy

Go through disks of guest, if one disk doesn't exist or its backing
chain is broken, with 'optional' startupPolicy, for CDROM and Floppy
we only discard its source path definition in xml, for disks we drop
it from disk list and free it.

include/libvirt/libvirt.h.in

@@ -4727,6 +4727,7 @@ typedef void (*virConnectDomainEventBlockJobCallback)(virConnectPtr conn,
  */
 typedef enum {
     VIR_DOMAIN_EVENT_DISK_CHANGE_MISSING_ON_START = 0, /* oldSrcPath is set */
+    VIR_DOMAIN_EVENT_DISK_DROP_MISSING_ON_START = 1,
 
 #ifdef VIR_ENUM_SENTINELS
     VIR_DOMAIN_EVENT_DISK_CHANGE_LAST

src/qemu/qemu_domain.c

@@ -2067,6 +2067,47 @@ cleanup:
     virObjectUnref(cfg);
 }
 
+static int
+qemuDomainCheckRemoveOptionalDisk(virQEMUDriverPtr driver,
+                                  virDomainObjPtr vm,
+                                  virDomainDiskDefPtr disk)
+{
+    char uuid[VIR_UUID_STRING_BUFLEN];
+    virDomainEventPtr event = NULL;
+    virDomainDiskDefPtr del_disk = NULL;
+
+    virUUIDFormat(vm->def->uuid, uuid);
+
+    VIR_DEBUG("Dropping disk '%s' on domain '%s' (UUID '%s') "
+              "due to inaccessible source '%s'",
+              disk->dst, vm->def->name, uuid, disk->src);
+
+    if (disk->device == VIR_DOMAIN_DISK_DEVICE_CDROM ||
+        disk->device == VIR_DOMAIN_DISK_DEVICE_FLOPPY) {
+
+        event = virDomainEventDiskChangeNewFromObj(vm, disk->src, NULL,
+                                                   disk->info.alias,
+                                                   VIR_DOMAIN_EVENT_DISK_CHANGE_MISSING_ON_START);
+        VIR_FREE(disk->src);
+    } else {
+        event = virDomainEventDiskChangeNewFromObj(vm, disk->src, NULL,
+                                                   disk->info.alias,
+                                                   VIR_DOMAIN_EVENT_DISK_DROP_MISSING_ON_START);
+
+        if (!(del_disk = virDomainDiskRemoveByName(vm->def, disk->src))) {
+            virReportError(VIR_ERR_INVALID_ARG,
+                           _("no source device %s"), disk->src);
+            return -1;
+        }
+        virDomainDiskDefFree(del_disk);
+    }
+
+    if (event)
+        qemuDomainEventQueue(driver, event);
+
+    return 0;
+}
+
 static int
 qemuDomainCheckDiskStartupPolicy(virQEMUDriverPtr driver,
                                  virDomainObjPtr vm,
@@ -2074,7 +2115,6 @@ qemuDomainCheckDiskStartupPolicy(virQEMUDriverPtr driver,
                                  bool cold_boot)
 {
     char uuid[VIR_UUID_STRING_BUFLEN];
-    virDomainEventPtr event = NULL;
     int startupPolicy = disk->startupPolicy;
 
     virUUIDFormat(vm->def->uuid, uuid);
@@ -2097,17 +2137,8 @@ qemuDomainCheckDiskStartupPolicy(virQEMUDriverPtr driver,
             break;
     }
 
-    virResetLastError();
-    VIR_DEBUG("Dropping disk '%s' on domain '%s' (UUID '%s') "
-              "due to inaccessible source '%s'",
-              disk->dst, vm->def->name, uuid, disk->src);
-
-    event = virDomainEventDiskChangeNewFromObj(vm, disk->src, NULL, disk->info.alias,
-                                               VIR_DOMAIN_EVENT_DISK_CHANGE_MISSING_ON_START);
-    if (event)
-        qemuDomainEventQueue(driver, event);
-
-    VIR_FREE(disk->src);
+    if (qemuDomainCheckRemoveOptionalDisk(driver, vm, disk) < 0)
+        goto error;
 
     return 0;
 
@@ -2125,8 +2156,8 @@ qemuDomainCheckDiskPresence(virQEMUDriverPtr driver,
     virDomainDiskDefPtr disk;
 
     VIR_DEBUG("Checking for disk presence");
-    for (i = 0; i < vm->def->ndisks; i++) {
-        disk = vm->def->disks[i];
+    for (i = vm->def->ndisks; i > 0; i--) {
+        disk = vm->def->disks[i - 1];
 
         if (!disk->src)
             continue;
@@ -2135,10 +2166,11 @@ qemuDomainCheckDiskPresence(virQEMUDriverPtr driver,
             qemuDiskChainCheckBroken(disk) >= 0)
             continue;
 
-        if (disk->startupPolicy) {
-            if (qemuDomainCheckDiskStartupPolicy(driver, vm, disk,
-                                                 cold_boot) >= 0)
-                continue;
+        if (disk->startupPolicy &&
+            qemuDomainCheckDiskStartupPolicy(driver, vm, disk,
+                                             cold_boot) >= 0) {
+            virResetLastError();
+            continue;
         }
 
         goto error;