savevm: Include writable devices with removable media

savevm and loadvm silently ignore block devices with removable media,
such as floppies and SD cards.  Rolling back a VM to a previous
checkpoint will *not* roll back writes to block devices with removable
media.

Moreover, bdrv_is_removable() is a confused mess, and wrong in at
least one case: it considers "-drive if=xen,media=cdrom -M xenpv"
removable.  It'll be cleaned up later in this series.

Read-only block devices are also ignored, but that's okay.

Fix by ignoring only read-only block devices and empty block devices.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/block.c b/block.c
index 487a6a954a..a8c789a079 100644
--- a/block.c
+++ b/block.c
@@ -2097,7 +2097,7 @@ void bdrv_debug_event(BlockDriverState *bs, BlkDebugEvent event)
 int bdrv_can_snapshot(BlockDriverState *bs)
 {
     BlockDriver *drv = bs->drv;
-    if (!drv || bdrv_is_removable(bs) || bdrv_is_read_only(bs)) {
+    if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
         return 0;
     }