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Date: Thu, 23 Aug 2012 12:03:32 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/2 v1] blkdrv: Add queue limits parameters
 for sg block drive
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To: Cong Meng <mc@linux.vnet.ibm.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, zwanp@cn.ibm.com, linuxram@us.ibm.com, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org

Il 23/08/2012 11:31, Cong Meng ha scritto:
>> For disks, this should be fixed simply by using scsi-block instead of
>> scsi-generic.
>>
>> CD-ROMs are indeed more complicated because burning CDs cannot be done
>> with syscalls. :/
> 
> So, as the problem exist to CD-ROM, I will continue to get these patches
> move on.

I'm still trying to understand the extent of the problem.

The problem occurs for _USB_ CD-ROMs according to Ben.  Passthrough of
USB storage devices should be done via USB passthrough, not virtio-scsi.
 If we do USB passthrough via the SCSI layer we miss on all the quirks
that the OS may do based on the USB product/vendor pairs.  There's no
end to these, and some of the quirks may cause the device to lock up or
corruption.

I'd rather see a reproducer using SAS/ATA/ATAPI disks before punting.

Paolo