virt-manager: Default to qcow2 on kvm

qcow2 enables fancy features like snapshots and is generally more
desktopy, which we purport to be.

We only do this on not horribly old libvirt/qemu, and only on qemu
connections. This may work for xen but I'm not going to turn it on
until someone tests it.

virtManager/addhardware.py

@@ -1346,7 +1346,7 @@ class vmmAddHardware(vmmGObjectUI):
             disk.driver_cache = cache
 
             if not fmt:
-                fmt = self.config.get_storage_format()
+                fmt = self.conn.get_default_storage_format()
                 if (self.is_default_storage() and
                     disk.get_vol_install() and
                     fmt in disk.get_vol_install().list_formats()):

virtManager/config.py

@@ -166,7 +166,7 @@ class vmmConfig(object):
         self.libvirt_packages = cliconfig.libvirt_packages
         self.askpass_package = cliconfig.askpass_package
         self.default_graphics_from_config = cliconfig.default_graphics
-        self.default_storage_format_from_config = "raw"
+        self.default_storage_format_from_config = "qcow2"
 
         self._objects = []
 
@@ -407,7 +407,7 @@ class vmmConfig(object):
     def set_graphics_type(self, gtype):
         self.conf.set("/new-vm/graphics-type", gtype.lower())
 
-    def get_storage_format(self, raw=False):
+    def get_default_storage_format(self, raw=False):
         ret = self.conf.get("/new-vm/storage-format")
         if ret not in ["default", "raw", "qcow2"]:
             ret = "default"

virtManager/connection.py

@@ -319,6 +319,18 @@ class vmmConnection(vmmGObject):
             os.mkdir(ret, 755)
         return ret
 
+    def get_default_storage_format(self):
+        raw = self.config.get_default_storage_format(raw=True)
+        if raw != "default":
+            return raw
+
+        fmt = self.config.get_default_storage_format()
+        if fmt != "qcow2":
+            return
+
+        if self.check_conn_support(self._backend.SUPPORT_CONN_DEFAULT_QCOW2):
+            return fmt
+        return None
 
     ####################################
     # Connection pretty print routines #

virtManager/create.py

@@ -1805,7 +1805,7 @@ class vmmCreate(vmmGObjectUI):
             disk.path = diskpath
             disk.set_create_storage(size=disksize, sparse=sparse)
 
-            fmt = self.config.get_storage_format()
+            fmt = self.conn.get_default_storage_format()
             if (self.is_default_storage() and
                 disk.get_vol_install() and
                 fmt in disk.get_vol_install().list_formats()):

virtManager/createvol.py

@@ -173,7 +173,7 @@ class vmmCreateVolume(vmmGObjectUI):
         if hasformat:
             # Select the default storage format
             self.widget("vol-format").set_active(0)
-            default = self.config.get_storage_format()
+            default = self.conn.get_default_storage_format()
             for row in self.widget("vol-format").get_model():
                 if row[0] == default:
                     self.widget("vol-format").set_active_iter(row.iter)

virtManager/preferences.py

@@ -153,7 +153,7 @@ class vmmPreferences(vmmGObjectUI):
 
     def refresh_storage_format(self):
         combo = self.widget("prefs-storage-format")
-        val = self.config.get_storage_format(raw=True)
+        val = self.config.get_default_storage_format(raw=True)
         uihelpers.set_row_selection(combo, val)
 
     def refresh_disk_poll(self):

virtinst/support.py

@@ -325,7 +325,11 @@ SUPPORT_CONN_LISTALLDEVICES = _make(function="virConnect.listAllDevices",
 SUPPORT_CONN_VIRTIO_MMIO = _make(version=1001002,
                                  drv_version=[("qemu", 1006000)])
 SUPPORT_CONN_DISK_SD = _make(version=1001002)
-
+# This is an arbitrary check to say whether it's a good idea to
+# default to qcow2. It might be fine for xen or qemu older than the versions
+# here, but until someone tests things I'm going to be a bit conservative.
+SUPPORT_CONN_DEFAULT_QCOW2 = _make(
+    version=8000, drv_version=[("qemu", 1002000), ("test", 0)])
 
 # Domain checks
 SUPPORT_DOMAIN_GETVCPUS = _make(function="virDomain.vcpus", args=())