On Wed, Mar 30, 2011 at 9:33 AM, Markus Armbruster <arm...@redhat.com> wrote: > Stefan Hajnoczi <stefa...@linux.vnet.ibm.com> writes: > >> This patch series fixes two Linux host CD-ROM pass-through bugs in QEMU. >> >> After applying these patches it is possible to pass-through a Linux host >> CD-ROM >> completely. The guest can eject from software or the physical eject button >> can >> be pressed on the drive. The guest can detect this and newly inserted media >> are noticed. There is no need to issue any QEMU monitor 'eject' or 'change' >> commands because the host CD-ROM is completely "passed through". > > Things can get confusing here, as "eject" is an overloaded term :) > > Let me try to preempt such confusion. We have three separate actions to > consider: OS opening and closing the tray, and QEMU monitor commands > "eject" and "change", and the user inserting/removing media from a > physical tray. > > On bare metal, OS open/close tray affects the physical tray the obvious > way. The user can insert/remove media while the tray is open. > > A virtual CD-ROM is backed by a QEMU block device (the things "info > block" shows). The block device can be empty (seen by the gues OS as > "no media"), or it can be connected to a file. Monitor commands "eject" > and "change" manipulate that connection. > > Guest OS open/close tray affects the virtual tray the obvious way. In > particular, if the OS opens, then closes the tray, it gets the same > media back, unless the user changed it[*]. > > Normally, a block device's file is an image file. Monitor commands > "eject" and "change" are seen by the guest OS as media change. > > Besides image files, we can also use host block devices. This adds > another way to change media: The user can insert/remove physical media > while the physical tray is open. > > Regardless, monitor commands "eject" and "change" still work, and are > still seen by the guest OS as media change.
I agree with your description. These patches improve Linux host CD-ROM pass-through. They do not help ISO CD-ROM weirdness but I'm interested in seeing what CD-ROM issues you're investigating. Stefan