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

[tgh <wwwwww4187@xxxxxxxxxxx>]

hi
does SCSI passthrough need hardware support ,such as VT-d, or not?if 
there are two device and two VMs, does it need VT-d support, or not ? 
can it run in PVmode or have to run in HVM mode?
Thanks in advance


Mark Williamson åé:
> 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
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >     
>
>
>   

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