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Re: [Qemu-devel] Re: [PATCH] virtio-blk: add SGI_IO passthru support

From: Christian Borntraeger
Subject: Re: [Qemu-devel] Re: [PATCH] virtio-blk: add SGI_IO passthru support
Date: Tue, 28 Apr 2009 18:52:13 +0200
User-agent: KMail/1.9.9

Am Tuesday 28 April 2009 18:37:01 schrieb Anthony Liguori:
> Christoph Hellwig wrote:
> >> Should we be 
> >> handling some SCSI cmds internally to QEMU (like eject operations) and 
> >> supporting media=cdrom in -drive for if=virtio?
> >>     
> >
> > Not quite yet.  Eventually I want to support a virtio-scsi kind of
> > transport which would use the same virtio-blk protocol but only send
> > scsi commands.  We'd need a different driver on the Linux side for
> > it that registers to the scsi layer.  On the QEMU side it could either
> > do pass-through to a real scsi device using SG_IO or use the existing
> > command scsi emulator in scsi-disk.c.
> >   
> Ah, excellent.  I think that's a great thing to do.  So do you think 
> virtio-scsi would deprecate virtio-blk?

There are lots of other block device drivers with strange characteristics. 
For example dasd/xpram disks with 4k block size or other disks with strange 
partitioning schemes. Doing a scsi emulation on top of these beasts looks 
possible but far from ideal. So I guess we will need virtio_blk for non-scsi 
block devices.


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