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Date: Tue, 5 Apr 2011 13:41:37 +0100
Message-ID: <BANLkTi=xHZbzd6DudW88YM-zOjxTXVWUGQ@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH v2 3/3] raw-posix: Re-open host CD-ROM after
	media change
From: Stefan Hajnoczi <stefanha@gmail.com>
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To: David Ahern <dsahern@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Juan Quintela <quintela@redhat.com>, libvir-list@redhat.com, qemu-devel@nongnu.org, Ryan Harper <ryanh@us.ibm.com>, Avi Kivity <avi@redhat.com>, Amit Shah <amit.shah@redhat.com>

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? =A0Or do they succeed and the size is j=
ust
>>>> reported incorrectly?
>>>>
>>>> If it's the later, I'd agree that it needs fixing in the kernel. =A0If
>>>> 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. =A0Is there a bug report for this? =A0What are the steps to repro=
duce 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