Re: [Qemu-devel][PATCH] Send unit_attention on cd-rom not_ready to ready transition

[Jamie Lokier <jamie@shareable.org>]

> > Patch sends a UNIT_ATTENTION(6), MEDIUM_MAY_HAVE_CHANGED(0x28) sense
> > when cdrom transitions from not ready to ready. 
> ...
> > Patch applies to SVN revision 4456.
> 
> I have checked that this code compiles, and it seems to make sense
> (although I haven't double-checked the SCSI specification to check
> whether this is the right place to send that UNIT ATTENTION message).

Is this expected to fix the following?

Running Windows XP guest, in the QEMU monitor I do "change ide1-cd0
none", then a little while later, "change ide1-cd0 newfile.iso".

Interestingly, Windows XP _does_ show the CD (drive D:) change from
having contents to being not present (after the first change command).

But after the second change command, Windows XP shows it changes to
having contents again - but the _old_ contents of the drive!

Using the "eject" QEMU monitor command doesn't help.

However, using the eject menu option from within Windows XP itself,
then changing the CD image QEMU's monitor - that does work and it
shows the new contents.

I'm thinking perhaps XP caches the disk contents, and even though it
sees the CD transition from present to not-present and back, it does
not flush it's cache for some (bizarre) reason.

Is this patch expected to fix this, so issuing the "change" command in
QEMU's monitor will cause XP to show the new contents?  Does that
imply _all_ CD drives issue the error shown in this patch?

Thanks,
-- Jamie