Re: [PATCH libibverbs V4 3/5] Use neighbour lookup for RoCE UD QPs Eth L2 resolution

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Sun, May 18, 2014 at 12:38:47PM +0300, Or Gerlitz wrote:
>  struct ibv_ah *__ibv_create_ah(struct ibv_pd *pd, struct ibv_ah_attr *attr)
>  {
> -	struct ibv_ah *ah = pd->context->ops.create_ah(pd, attr);
> +	int err;
> +	struct ibv_ah *ah = NULL;
> +#ifndef NRESOLVE_NEIGH
> +	struct ibv_port_attr port_attr;
> +	int dst_family;
> +	int src_family;
> +	int oif;
> +	struct get_neigh_handler neigh_handler;
> +	union ibv_gid sgid;
> +	struct ibv_ah_attr_ex attr_ex;
> +	int ether_len;
> +	struct verbs_context *vctx = verbs_get_ctx_op(pd->context,
> +						      create_ah_ex);
> +	struct peer_address src;
> +	struct peer_address dst;
> +
> +	if (!vctx) {
> +#endif
> +		ah = pd->context->ops.create_ah(pd, attr);
> +#ifndef NRESOLVE_NEIGH
> +		goto return_ah;
> +	}
> +
> +	err = ibv_query_port(pd->context, attr->port_num, &port_attr);

It feels like a regression to force this overhead. Many HCAs have no
possibility to support anything but IB, or Ethernet and don't need
this.

This whole arrangement seems strange. create_ah_ex should be a full
fledged user callable function, not a buried driver entry point.
It is also very unusual for verbs to have all this generic code in
a driver wrapper.

I suspect the answer here is to have the driver call into helper
functions from verbs to do this addressing
work. 'get_ethernet_l2_from_ah' or something.

If you do that then we don't even need create_ah_ex and query_port_ex
- those function seem to only be required to support this wrapper
technique.

So please rethink how this flows.. Maybe wrapping is not the best
choice??

Jason
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