Re: [PATCH 1/2 v1] blkdrv: Add queue limits parameters for sg block drive

[Paolo Bonzini <pbonzini@redhat.com>]

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