Perform disk config validity checking for attach-device config

https://bugzilla.redhat.com/show_bug.cgi?id=1078126

Using 'virsh attach-device --config' (or --persistent) to attach a
file backed lun device will succeed; however, subsequent domain restarts
will result in failure because the configuration of a file backed lun
is not supported.

Although allowing 'illegal configurations' is something that can be
allowed, it may not be practical in this case. Generally, when attaching
a device to a domain means the domain must be running. A way around
this is using the --config (or --persistent) option. When an attach
is done to a running domain, a temporary configuration is modified
first followed by the live update. The live update will make a number
of disk validity checks when building the qemu command to attach the
disk. If any fail, then change is rejected.

Rather than allow a potentially illegal combination, adjust the code
in the configuration path to make the same checks as the running path
will make with respect to disk validity checks. This way we avoid
having the potential for some subsequent start/reboot to fail because
an illegal combination was allowed.

NB: The live path still checks the configuration since it is possible
to just do --live guest modification...

src/qemu/qemu_command.c

@@ -3216,6 +3216,73 @@ qemuGetDriveSourceString(virStorageSourcePtr src,
 }
 
 
+/* Perform disk definition config validity checks */
+int
+qemuCheckDiskConfig(virDomainDiskDefPtr disk)
+{
+    if (virDiskNameToIndex(disk->dst) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("unsupported disk type '%s'"), disk->dst);
+        goto error;
+    }
+
+    if (disk->wwn) {
+        if ((disk->bus != VIR_DOMAIN_DISK_BUS_IDE) &&
+            (disk->bus != VIR_DOMAIN_DISK_BUS_SCSI)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("Only ide and scsi disk support wwn"));
+            goto error;
+        }
+    }
+
+    if ((disk->vendor || disk->product) &&
+        disk->bus != VIR_DOMAIN_DISK_BUS_SCSI) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("Only scsi disk supports vendor and product"));
+            goto error;
+    }
+
+    if (disk->device == VIR_DOMAIN_DISK_DEVICE_LUN) {
+        /* make sure that both the bus supports type='lun' (SG_IO). */
+        if (disk->bus != VIR_DOMAIN_DISK_BUS_VIRTIO &&
+            disk->bus != VIR_DOMAIN_DISK_BUS_SCSI) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("disk device='lun' is not supported for bus='%s'"),
+                           virDomainDiskQEMUBusTypeToString(disk->bus));
+            goto error;
+        }
+        if (disk->src->type == VIR_STORAGE_TYPE_NETWORK) {
+            if (disk->src->protocol != VIR_STORAGE_NET_PROTOCOL_ISCSI) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("disk device='lun' is not supported "
+                                 "for protocol='%s'"),
+                               virStorageNetProtocolTypeToString(disk->src->protocol));
+                goto error;
+            }
+        } else if (!virDomainDiskSourceIsBlockType(disk->src)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("disk device='lun' is only valid for block "
+                             "type disk source"));
+            goto error;
+        }
+        if (disk->wwn) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("Setting wwn is not supported for lun device"));
+            goto error;
+        }
+        if (disk->vendor || disk->product) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("Setting vendor or product is not supported "
+                             "for lun device"));
+            goto error;
+        }
+    }
+    return 0;
+ error:
+    return -1;
+}
+
+
 char *
 qemuBuildDriveStr(virConnectPtr conn,
                   virDomainDiskDefPtr disk,
@@ -3602,68 +3669,18 @@ qemuBuildDriveDevStr(virDomainDefPtr def,
 {
     virBuffer opt = VIR_BUFFER_INITIALIZER;
     const char *bus = virDomainDiskQEMUBusTypeToString(disk->bus);
-    int idx = virDiskNameToIndex(disk->dst);
     int controllerModel;
 
-    if (idx < 0) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("unsupported disk type '%s'"), disk->dst);
+    if (qemuCheckDiskConfig(disk) < 0)
         goto error;
-    }
-
-    if (disk->wwn) {
-        if ((disk->bus != VIR_DOMAIN_DISK_BUS_IDE) &&
-            (disk->bus != VIR_DOMAIN_DISK_BUS_SCSI)) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("Only ide and scsi disk support wwn"));
-            goto error;
-        }
-    }
-
-    if ((disk->vendor || disk->product) &&
-        disk->bus != VIR_DOMAIN_DISK_BUS_SCSI) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("Only scsi disk supports vendor and product"));
-            goto error;
-    }
 
+    /* Live only checks */
     if (disk->device == VIR_DOMAIN_DISK_DEVICE_LUN) {
-        /* make sure that both the bus and the qemu binary support
-         *  type='lun' (SG_IO).
-         */
-        if (disk->bus != VIR_DOMAIN_DISK_BUS_VIRTIO &&
-            disk->bus != VIR_DOMAIN_DISK_BUS_SCSI) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                           _("disk device='lun' is not supported for bus='%s'"),
-                           bus);
-            goto error;
-        }
-        if (disk->src->type == VIR_STORAGE_TYPE_NETWORK) {
-            if (disk->src->protocol != VIR_STORAGE_NET_PROTOCOL_ISCSI) {
-                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                               _("disk device='lun' is not supported for protocol='%s'"),
-                               virStorageNetProtocolTypeToString(disk->src->protocol));
-                goto error;
-            }
-        } else if (!virDomainDiskSourceIsBlockType(disk->src)) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("disk device='lun' is only valid for block type disk source"));
-            goto error;
-        }
+        /* make sure that the qemu binary supports type='lun' (SG_IO). */
         if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_VIRTIO_BLK_SG_IO)) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("disk device='lun' is not supported by this QEMU"));
-            goto error;
-        }
-        if (disk->wwn) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("Setting wwn is not supported for lun device"));
-            goto error;
-        }
-        if (disk->vendor || disk->product) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("Setting vendor or product is not supported "
-                             "for lun device"));
+                           _("disk device='lun' is not supported by "
+                             "this QEMU"));
             goto error;
         }
     }

src/qemu/qemu_command.h

@@ -271,4 +271,6 @@ qemuParseKeywords(const char *str,
 int qemuGetDriveSourceString(virStorageSourcePtr src,
                              virConnectPtr conn,
                              char **source);
+
+int qemuCheckDiskConfig(virDomainDiskDefPtr disk);
 #endif /* __QEMU_COMMAND_H__*/

src/qemu/qemu_driver.c

@@ -6737,6 +6737,8 @@ qemuDomainAttachDeviceConfig(virQEMUCapsPtr qemuCaps,
                            _("target %s already exists"), disk->dst);
             return -1;
         }
+        if (qemuCheckDiskConfig(disk) < 0)
+            return -1;
         if (virDomainDiskInsert(vmdef, disk))
             return -1;
         /* vmdef has the pointer. Generic codes for vmdef will do all jobs */