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[Qemu-devel] CD-ROM bug round-up

From: Stefan Hajnoczi
Subject: [Qemu-devel] CD-ROM bug round-up
Date: Wed, 30 Mar 2011 17:40:40 +0100

Several of us have been investigating CD-ROM bugs.  Let's update each
other, make sure we're not duplicating effort, and see if we can help
each other make progress.

= Stefan =

Guests do not notice media change when using Linux host CD-ROM
pass-through for two reasons:
1. QEMU is caching the device size for removable media and never updating it.
2. On Linux hosts the /dev/cdrom file descriptor needs to be reopened
to refresh the underlying device size.

Patches have been posted to qemu-devel.

Libvirt does not recognize eject failure due to locked tray.  This
causes libvirt to get out-of-sync and believe the medium was
successfully changed.  A libvirt fix is in progress:

= Anthony =

Using 'change' or scripted commands without a delay between closing
the BlockDriverState and opening the new CD-ROM.  The guest does not
have a chance to poll the drive and determine a medium present ->
medium not present transition followed by a medium not present ->
medium present transition.

A fix for this does not exist yet and might be tricky since we need to
delay or wait for the guest to poll once before opening the new

= Amit =

Found that 2.6.38 and later guest kernels fail to report media change.
 The new in-kernel media change polling framework issues ATAPI
commands which are not implemented in hw/ide/core.c.

= Juan =

ATA HSM violation errors after live migration while CD-ROM read
operations.  This is probably a hw/ide/* or DMA migration bug.

= Markus =



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