qemu: domain: Forbid storage type 'cow' in qemu

QEMU does not support it so save us the hassle and forbid it right away.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>

src/qemu/qemu_domain.c

@@ -4108,9 +4108,24 @@ qemuDomainDeviceDefValidateVideo(const virDomainVideoDef *video)
 }
 
 
+static int
+qemuDomainValidateStorageSource(virStorageSourcePtr src)
+{
+    if (src->format == VIR_STORAGE_FILE_COW) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                      _("'cow' storage format is not supported"));
+        return -1;
+    }
+
+    return 0;
+}
+
+
 static int
 qemuDomainDeviceDefValidateDisk(const virDomainDiskDef *disk)
 {
+    virStorageSourcePtr n;
+
     if (disk->src->shared && !disk->src->readonly) {
         if (disk->src->format <= VIR_STORAGE_FILE_AUTO) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
@@ -4127,6 +4142,11 @@ qemuDomainDeviceDefValidateDisk(const virDomainDiskDef *disk)
         }
     }
 
+    for (n = disk->src; virStorageSourceIsBacking(n); n = n->backingStore) {
+        if (qemuDomainValidateStorageSource(n) < 0)
+            return -1;
+    }
+
     return 0;
 }
 
@@ -11837,6 +11857,9 @@ qemuDomainPrepareDiskSourceChain(virDomainDiskDefPtr disk,
             n->debug = true;
             n->debugLevel = cfg->glusterDebugLevel;
         }
+
+        if (qemuDomainValidateStorageSource(n) < 0)
+            return -1;
     }
 
     return 0;

tests/qemuxml2argvdata/disk-drive-fmt-cow.xml

+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <devices>
+    <emulator>/usr/bin/qemu-system-i686</emulator>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='cow'/>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='none'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -912,6 +912,7 @@ mymain(void)
             QEMU_CAPS_NODEFCONFIG);
     DO_TEST("disk-drive-fmt-qcow",
             QEMU_CAPS_DRIVE_BOOT);
+    DO_TEST_PARSE_ERROR("disk-drive-fmt-cow", QEMU_CAPS_DRIVE_BOOT);
     DO_TEST("disk-drive-shared",
             QEMU_CAPS_DRIVE_SERIAL);
     DO_TEST_PARSE_ERROR("disk-drive-shared-qcow", NONE);