Re: [Qemu-devel] Do you have a use for a tester of virtio-scsi with CD drives ?

[Paolo Bonzini]

On 11/07/2011 11:04 AM, Thomas Schmitt wrote:
> In a thread on linux-hotplug, /dev/sg* is declared to be deprecated
> in favor of/dev/bsg/* and /dev/sr*.
> Will this become a problem ?

I think /dev/bsg is backwards-compatible more or less, but it would help
if it had decent documentation in the kernel tree.

> I did not succeed with googling for a way to get a block device
> running on top of file=/dev/sg*,if=virtio.

No, that's not possible with /dev/sg.  But I think this helps:

   -drive file=/dev/sr0,if=none,id=scsicd
   -device 
virtio-blk,drive=scsicd,logical_block_size=2048,physical_block_size=2048

At least here, dd works with this command line.  This probably will
be fixed in QEMU 1.1 (i.e. the release after the next one).

> The word "passthrough" does not show up in the context of drive
> emulation in any documentation inside the git clone.
> I only see statements about:  "passthrough" security model.
> The word "virtio" is mentioned more often, but without much explanation
> of -drive use cases and pitfalls. (Only docs/qdev-device-use.txt
> has some more detailed information.)

Yes, docs/qdev-device-use.txt helps.  "qemu -device virtio-blk,?" too.

> Is there an external documentation emerging ?
> I would like to read it and contribute my experiences.

Hopefully, everything would just work. :)

You can work on wiki.qemu.org in the meanwhile.

Paolo