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Date: Wed, 02 Nov 2011 17:34:03 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] Do you have a use for a tester of virtio-scsi with
 CD drives ?
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To: Thomas Schmitt <scdbackup@gmx.net>
Cc: kwolf@redhat.com, stefanha@gmail.com, qemu-devel@nongnu.org

On 11/02/2011 05:26 PM, Thomas Schmitt wrote:
> Hi,
>
> Paolo Bonzini wrote:
>> I suggest trying with 1.0-rc (origin/master).
>
> Am i on the right track with  git clone git://git.qemu.org/qemu.git  ?

Yes.

>> scsi-block uses
>> read+write for READ/WRITE CDBs and SG_IO for everything else.
>
> That sounds scary to me. On real Linux systems it is not advisable to
> mix SG_IO and block device driver. At least not with optical media.
> Often the block device does not learn about status changes until
> the tray gets ejected and reloaded manually or by the block device
> driver. If i load it by START/STOP UNIT via SG_IO, then the block
> device driver believes there are no readable blocks on the medium.

Ah, I didn't know this.  Probably it's because I didn't test on a 
machine with a tray that can load, only a laptop.  We certainly can 
switch more commands from pass-through to emulated (including START/STOP 
UNIT).

Paolo