Re: [PATCH 6/6] virtio-scsi: Enable DIF/DIX modes in SCSI host LLD

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, May 19, 2014 at 12:07:03PM -0700, Nicholas A. Bellinger wrote:
> On Wed, 2014-05-07 at 12:13 +0300, Michael S. Tsirkin wrote:
> > On Mon, Apr 07, 2014 at 01:56:59AM -0700, Nicholas A. Bellinger wrote:
> > > On Mon, 2014-04-07 at 11:45 +0300, Michael S. Tsirkin wrote:
> > > > On Sun, Apr 06, 2014 at 09:32:09PM +0000, Nicholas A. Bellinger wrote:
> > > > > From: Nicholas Bellinger <nab@linux-iscsi.org>
> > > > > 
> > > > > This patch updates virtscsi_probe() to setup necessary Scsi_Host
> > > > > level protection resources. (currently hardcoded to 1)
> > > > > 
> > > > > It changes virtscsi_add_cmd() to attach outgoing / incoming
> > > > > protection SGLs preceeding the data payload, and is using the
> > > > > new virtio_scsi_cmd_req_pi->d[oi],pi_niv field to signal
> > > > > to signal to vhost/scsi how many prot_sgs to expect.
> > > > > 
> > > > > v3 changes:
> > > > >   - Use VIRTIO_SCSI_F_T10_PI to determine PI or non PI header (Paolo)
> > > > > 
> > > > > v2 changes:
> > > > >   - Make protection buffer come before data buffer (Paolo)
> > > > >   - Enable virtio_scsi_cmd_req_pi usage (Paolo)
> > > > > 
> > > > > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > > > > Cc: Michael S. Tsirkin <mst@redhat.com>
> > > > > Cc: Martin K. Petersen <martin.petersen@oracle.com>
> > > > > Cc: Christoph Hellwig <hch@lst.de>
> > > > > Cc: Hannes Reinecke <hare@suse.de>
> > > > > Cc: Sagi Grimberg <sagig@dev.mellanox.co.il>
> > > > > Cc: H. Peter Anvin <hpa@zytor.com>
> > > > > Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> > > > 
> > > > OK but we need to document the new interface in the spec
> > > > (and incidentially, this will be useful to verify the assumptions
> > > > made here and on the host side).
> > > > Could you please submit this proposal to the OASIS Virtio TC
> > > > for inclusion into the next spec draft?
> > > > Ideally as a patch against the tex source, but a prose
> > > > description would do as well.
> > > 
> > > Most certainly.  Please give me a bit to follow up on this, as the next
> > > couple of days are going to be hellishly busy..
> > 
> > Ping.
> > We really need to get this moving to have the interface reviewed for
> > the next merge window.
> > 
> 
> Hi MST,
> 
> So I've finally got some cycles to get back to this code, and wanted to
> verify the outstanding items you had previously raised:
> 
> - Convert vhost-scsi to be independent of IOV layout using 
>   memcpy_fromiovecend. (Does this effect existing non PI virtio-scsi 
>   operation..?)

Ideally yes.

> - Report VIRTIO_F_ANY_LAYOUT feature bit to userspace.
> - Convert virtio_scsi_cmd_req_pi to bytes field instead of number of 
>   iovecs.
> - Ensure virtio_scsi_cmd_req_pi is naturally aligned

It turns out other virtio scsi commands aren't aligned?
If true we don't need to make an exception here.

> - Figure out why QEMU is not acking (any) vhost-scsi feature bits
> 
> Is there anything else that you'd like to see for an initial merge, or
> other issues that need to be addressed with the above..?
> 
> --nab

FYI Paolo sent a spec patch for the feature.
Have you seen it?

-- 
MST