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Re: [libvirt] [Qemu-devel] [PATCH v2 3/3] raw-posix: Re-open host CD-ROM after media change



On Tue, Apr 5, 2011 at 6:42 AM, David Ahern <dsahern gmail com> wrote:
> On 04/04/11 23:33, Stefan Hajnoczi wrote:
>> On Mon, Apr 4, 2011 at 6:54 PM, David Ahern <dsahern gmail com> wrote:
>>> On 04/04/11 07:38, Anthony Liguori wrote:
>>>> On 04/04/2011 08:22 AM, Avi Kivity wrote:
>>>>> On 04/03/2011 02:57 PM, Stefan Hajnoczi wrote:
>>>>>> In order for media change to work with Linux host CD-ROM it is
>>>>>> necessary to reopen the file (otherwise the inode size will not
>>>>>> refresh, this is an issue with existing kernels).
>>>>>>
>>>>>
>>>>> Maybe we should fix the bug in Linux (and backport as necessary)?
>>>>>
>>>>> I think cd-rom assignment is sufficiently obscure that we can require
>>>>> a fixed kernel instead of providing a workaround.
>>>>
>>>> Do reads fail after CD change?  Or do they succeed and the size is just
>>>> reported incorrectly?
>>>>
>>>> If it's the later, I'd agree that it needs fixing in the kernel.  If
>>>> it's the former, I'd say it's clearly a feature.
>>>
>>> In January 2010 I was seeing old data -- data from the prior CD -- in
>>> the guest after the media change.
>>
>> Yikes.  Is there a bug report for this?  What are the steps to reproduce it?
>
> Not that I know of. It is reported by someone else last year as well:
> http://www.mail-archive.com/kvm vger kernel org/msg32999.html

Thanks for the link.  That looks like typical symptoms of missing
media change (which can also legitimately happen if the guest does not
poll).  This should be fixed once the CD-ROM fixes are merged into
QEMU and Linux.

Stefan


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