On Thu, Aug 23, 2012 at 11:03 AM, Paolo Bonzini <pbonz...@redhat.com> wrote: > 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.
This issue affects passthrough: either an entire sg device or at least a SG_IO ioctl (e.g. a non-READ/WRITE SCSI command). To reproduce it, check host queue limits and guest virtio-scsi queue limits. Then pick a command that can exceed the limits and try it from inside the guest :). Stefan
