Re: [Xen-devel] SCSI passthrough using /dev/sgX

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

There are some folks (from Fujitsu?  I think?) who are working on 
front/back-based SCSI passthrough.  Patches have been submitted several times 
but not merged yet.  They'll be in the list archives...

I don't think they've done a Windows frontend though ;-)

Cheers,
Mark

On Tuesday 04 December 2007, James Harper wrote:
> > Is anyone working on SCSI passthrough using the 'SCSI Generic' support
> > under Linux, eg /dev/sgX? This is how VMWare allows a VM to use SCSI
> > devices.
>
> I assume that the lack of response means 'no'.
>
> I've just been having a look through the documentation for 'SCSI
> Generic' under Linux, and it looks pretty straightforward...
>
> It could be done much like the existing blkdev interface, the 'input'
> half of the sg_io_hdr (or something like it), would go on the ring as
> the request, and the 'output' half, would come back on the ring as the
> response. Buffers would be passed like the block interface does now,
> although I'd probably prefer that we allow single byte aligned rather
> than 512 byte aligned buffers as the block device currently does, as
> Windows tends to use the former a bit. I'm not sure if any other IOCTL's
> apart from SG_IO (which is the equivalent of a write + read operation
> anyway) would be required as part of normal IO, they could just be
> performed at initialisation and written to xenstore.
>
> This would allow single SCSI devices or pretty much any type to be
> exported to domains.
>
> I'm interested in writing the Linux backend, and the Windows front end
> as I'm pretty desperate for tape drive passthrough...
>
> Comments?
>
> Thanks
>
> James
>
>
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-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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