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

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

On Tue, Sep 1, 2009 at 6:12 PM, Roland Dreier <rdreier@cisco.com> wrote:
>  > - 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).
>
> I don't think this really makes sense, because IPoIB is not really
> handling ethernet (it is a different L2 ethernet encapsulation), and I
> think the commonality with ibmveth is going to be minimal.

What I had in mind was not to start searching for code shared between
the ipoib and ibmveth kernel modules, but to replace the virtual
Ethernet layer by IPoIB on top of a new RDMA driver. I'm not sure
however this approach would work better than the currently implemented
approach in ibmveth.

> I'm not really sure we should be trying to force drivers to share just
> because they are paravirtualized -- if there is real commonality, then
> sure put it in common code, but different hypervisors are probably as
> different as different hardware.

Agreed. But several people are currently looking at how to improve the
performance of I/O performed inside a virtual machine without being
familiar with the VIA architecture or the RDMA API. This is a pity
because the Virtual Interface Architecture was designed to allow
high-throughput low-latency I/O, and has some features that are not
present in any other mainstream I/O architecture I know of (e.g. the
ability to perform I/O from userspace without having to invoke any
system call in the performance-critical path).

Bart.