[Qemu-devel] [Bug 1070762] Re: savevm fails with inserted CD, "Device '%s' is writable but does not support snapshots."

[John Snow <1070762@bugs.launchpad.net>]

** Changed in: qemu
     Assignee: (unassigned) => John Snow (jnsnow)

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https://bugs.launchpad.net/bugs/1070762

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

Status in QEMU:
  New

Bug description:
  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.

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