On Fri, Dec 04, 2009 at 08:03:31PM -0800, Roland Dreier wrote:
>
> > Yes, every Linux arch aligns structs to the min alignment for the
> > members, so at least 32 in this case.
> >
> > However, it doesn't really matter, look at ibv_cmd_query_port, it
> > doesn't zero the padding. So there must be an ABI bump to ensure that
> > new code links to a library that doesn't fill the new member with
> > garbage.
> >
> > This is a messy one, the low level libraries have to be reved somehow too..
> > ops.query_port2() I guess.
>
> Actually I think we can fix this in libibverbs without having to break
> anything. It's a little bit devious, but if we do something like:
>
> // ... add link_layer member in padding of struct ibv_port_attr
>
> enum {
> IBV_LINK_LAYER_UNSPECIFIED,
> IBV_LINK_LAYER_INFINIBAND,
> IBV_LINK_LAYER_ETHERNET,
> };
>
> static inline int __ibv_query_port(struct ibv_context *context, uint8_t
> port_num,
> struct ibv_port_attr *port_attr)
> {
> port_attr->link_layer = IBV_LINK_LAYER_UNSPECIFIED;
> return ibv_query_port(context, port_num, port_attr);
> }
>
> // ... rest of file...
>
> #define ibv_query_port(context, port_num, port_attr) \
> __ibv_query_port(context, port_num, port_attr)
>
> then I think legacy apps should be OK (port_attr size doesn't change,
> binary compat is still there), and new apps that do check link_layer
> should also be OK ... if they use an old library and/or old driver,
> they'll see LINK_LAYER_UNSPECIFIED, which means that IBoE is not supported.
>
> What do you think, does this work?
>
> - R.
It looks good to me. Thanks, I will take it for RDMAoE.
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