Re: [PATCH v5 4/4] RDMA/cma: Avoid GID lookups on iWARP devices

[Jason Gunthorpe <jgg@nvidia.com>]

On Sat, Jul 01, 2023 at 04:27:23PM +0000, Chuck Lever III wrote:
> 
> 
> > On Jul 1, 2023, at 12:24 PM, Tom Talpey <tom@talpey.com> wrote:
> > 
> > On 6/29/2023 11:16 AM, Chuck Lever wrote:
> >> From: Chuck Lever <chuck.lever@oracle.com>
> >> We would like to enable the use of siw on top of a VPN that is
> >> constructed and managed via a tun device. That hasn't worked up
> >> until now because ARPHRD_NONE devices (such as tun devices) have
> >> no GID for the RDMA/core to look up.
> >> But it turns out that the egress device has already been picked for
> >> us -- no GID is necessary. addr_handler() just has to do the right
> >> thing with it.
> >> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> >> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> >> ---
> >>  drivers/infiniband/core/cma.c |   15 +++++++++++++++
> >>  1 file changed, 15 insertions(+)
> >> diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
> >> index 889b3e4ea980..07bb5ac4019d 100644
> >> --- a/drivers/infiniband/core/cma.c
> >> +++ b/drivers/infiniband/core/cma.c
> >> @@ -700,6 +700,21 @@ cma_validate_port(struct ib_device *device, u32 port,
> >>   if ((dev_type != ARPHRD_INFINIBAND) && rdma_protocol_ib(device, port))
> >>   goto out;
> >>  + /* Linux iWARP devices have but one port */
> > 
> > I don't believe this comment is correct, or necessary. In-tree drivers
> > exist for several multi-port iWARP devices, and the port bnumber passed
> > to rdma_protocol_iwarp() and rdma_get_gid_attr() will follow, no?
> 
> Then I must have misunderstood what Jason said about the reason
> for the rdma_protocol_iwarp() check. He said that we are able to
> do this kind of GID lookup because iWARP devices have only a
> single port.
> 
> Jason?

I don't know alot about iwarp - tom does iwarp really have multiported
*struct ib_device* models? This is different from multiport hw.

If it is multiport how do the gid tables work across the ports?

Jason