savevm fails with inserted CD, "Device '%s' is writable but does not support snapshots."

[Oliver Francke]

Hi,

yesterday unfortunately a customer reported a failed snapshot of his VM. Going through the logfile I discovered:

"Device 'ide1-cd0' is writable but does not support snapshots"

this is with qemu-1.2.0 and 1.0.1 at least...

Why writeable?
Even if I specify "-drive ...,readonly=on,snapshot=off" to qemu the monitor-command sees the CD-ROM-device as being writeable?!

Somewhere I saw a "hint" for blockdev.c:
=== snip ===

--- /tmp/blockdev.c 2012-10-24 11:37:10.000000000 +0200
+++ blockdev.c 2012-10-24 11:37:17.000000000 +0200
@@ -551,6 +551,7 @@
     case IF_XEN:
     case IF_NONE:
         dinfo->media_cd = media == MEDIA_CDROM;
+ dinfo->bdrv->read_only = 1;
         break;
     case IF_SD:
     case IF_FLOPPY:

=== snap ===

after installing with this small patch applied it works, so insert CD, savevm <somename> succeeds.
This should be fixed at all correct places, and the tags "readonly=on,snapshot=off" should do it, too. Or even just work after specifying a drive being a CD-rom should do the trick ;-)

Another "bad habit" is, that the ISO/DVD-file has to be writeable to be changed?

Thnx for attention and regards,

Oliver.

[John Snow (jnsnow)]

Very old bug. If anyone sees this behavior, please re-file against a supported release (5.0 at time of writing, soon to be 5.1) and please paste a full command-line and steps to reproduce.

(To my knowledge, this bug is not present in modern QEMU builds, but do not know when it would have changed.)

--js

[Launchpad Janitor (janitor)]

[Expired for QEMU because there has been no activity for 60 days.]