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

[Bart Van Assche <bvanassche@acm.org>]

On Mon, Aug 31, 2009 at 8:00 PM, James Bottomley
<James.Bottomley@suse.de> 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?

Good question. But shouldn't the ibmvscsi driver be refactored before
considering sharing ibmvscsi code with other paravirtualized drivers ?
A quote from the ibmvscsi.c source code:

 * TODO: This is currently pretty tied to the IBM i/pSeries hypervisor
 * interfaces.  It would be really nice to abstract this above an RDMA
 * layer.

Splitting the ibmvscsi.c driver in an SRP initiator and an RDMA driver
would make the following possible:
- Reuse the existing SRP initiator (ib_srp). Currently there are two
SRP initiators present in the Linux kernel -- one that uses the RDMA
verbs API (ib_srp) and one that only works with IBM's i/pSeries
hypervisor (ibmvscsi).
- Reuse the ib_ipoib kernel module to provide an IP stack on top of
the new RDMA driver instead of having to maintain a separate network
driver for this hardware (ibmveth).

More information about the architecture the ibmvscsi and the ibmveth
drivers have been developed for can be found in the following paper:
D. Boutcher and D. Engebretsen, Linux Virtualization on IBM POWER5
Systems, Proceedings of the Linux Symposium, Vol. 1, July 2004, pp.
113-120 (http://www.kernel.org/doc/mirror/ols2004v1.pdf).

Bart.