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Re: [Libguestfs] [PATCH] Fix broken qemu <= 0.10 which randomly adds a CD-ROM device to the appliance



On Thu, Jul 30, 2009 at 09:14:07AM +0100, Matthew Booth wrote:
> On 29/07/09 15:08, Richard W.M. Jones wrote:
>> qemu<= 0.10 randomly adds a CD-ROM device to the appliance because of
>> this bit of code:
>>
>> http://git.savannah.gnu.org/cgit/qemu.git/tree/vl.c?h=stable-0.10#n5495
>>
>
> I'm not convinced this is the right fix. list_devices is supposed to  
> list devices, and for good or ill, the CD-ROM device is present.

If the caller called add_cdrom then the CD-ROM device would be both
present _and_ contain media, so it would show up in the list.

There's no way that I know of to add a CD-ROM file without media using
an explicit qemu command line parameter.  AFAIK such devices can only
be added by this qemu stupidity.

> What is the contract of list_devices supposed to be?

My expectation has been that it would list the devices which were
added using add_drive* / add_cdrom calls.  Certainly not that it would
list those devices, plus some other random devices that qemu pulled
out of thin air.

We (sorta) enforced this contract by adding an explicit test that this
was the case, and this test started to break when we had a version of
qemu which was adding its own random CD-ROM device.

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
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