Re: [Qemu-devel] Re: To O_EXCL or not to O_EXCL open host_cdrom

[Avi Kivity]

On 04/11/2011 11:31 AM, Stefan Hajnoczi wrote:
> On Mon, Apr 11, 2011 at 10:37:32AM +0530, Amit Shah wrote:
> >  On (Fri) 08 Apr 2011 [12:33:27], Stefan Hajnoczi wrote:
> >  >  The other concern I have about using O_EXCL is that we expose
> >  >  ourselves to race conditions if there is ever a need to re-open the
> >  >  device.  When QEMU closes its file descriptor another program may be
> >  >  scheduled to run and open the device with O_EXCL.  Now QEMU will not
> >  >  be able to open the CD-ROM anymore.
> >
> >  The admins should really be the ones worrying about this, not QEMU.
>
> Think of a desktop use case.  virt-manager lets me pass through the host
> CD-ROM today.  Desktops have hald/udisks and you can't expect users to
> disable/reenable those services just for QEMU.

It should be solved at that level then.  If I insert a disc into an 
assigned cd-rom drive, I shouldn't get a file manager or autorun window 
to pop in the host, just the guest.

So: libvirt should inform the rest of the system that it is taking over 
the cd-rom and as far as they're concerned, it no longer exists.

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