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Message-Id: <1251815012.3864.55.camel@mulgrave.site>
Date: Tue, 01 Sep 2009 09:23:32 -0500
From: James Bottomley <James.Bottomley@...e.de>
To: akataria@...are.com
Cc: Robert Love <robert.w.love@...el.com>,
Randy Dunlap <randy.dunlap@...cle.com>,
Mike Christie <michaelc@...wisc.edu>,
"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Dmitry Torokhov <dtor@...are.com>,
Rolf Eike Beer <eike-kernel@...tec.de>,
Maxime Austruy <maustruy@...are.com>,
Bhavesh Davda <bhavesh@...are.com>
Subject: Re: [PATCH] SCSI driver for VMware's virtual HBA.
On Mon, 2009-08-31 at 14:53 -0700, Alok Kataria wrote:
> Hi James,
>
> Thanks for your comments.
>
> On Mon, 2009-08-31 at 11:00 -0700, James Bottomley wrote:
> > On Mon, 2009-08-31 at 10:28 -0700, Alok Kataria wrote:
> > > VMware PVSCSI driver - v2.
> >
> > OK, so the first thing that springs to mind is that we already have one
> > of these things: the ibmvscsi ... is there no way we can share code
> > between this and the other PV drivers?
>
> I took a quick look at the ibmvscsi driver, and there are lot of
> differences between the two, mainly the ABI that is shared between the
> hypervisor and driver differ.
Well, that's pretty abstractable, surely? However, there is an
interesting question of what the best hypervisor interface actually is.
> Also the ibmvscsi driver seems to offer a
> lot of other features as well, like the SRP.
SRP is the protocol transfer abstraction. It's just a way of packaging
up SCSI commands for transfer over a DMA protocol (OK, so it was
envisaged that the DMA protocol would be RDMA, but a hypervisor
interface is also a DMA protocol).
> The pvscsi driver is a simple SCSI adapter driver and is basically no
> different than any other SCSI driver written for a particular HBA.
Well, it is really ... hopefully all the hypervisor interfaces won't
decide to be completely incompatible, so there's a good chance of code
sharing between them.
James
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