Re: [PATCH] SCSI driver for VMware's virtual HBA.

[James Bottomley <James.Bottomley@suse.de>]

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