Re: [PATCH] Add missing ib_uverbs dependency from SoftiWARP

[Tom Talpey <tom@talpey.com>]

On 9/7/2022 9:51 AM, Jason Gunthorpe wrote:
> On Wed, Sep 07, 2022 at 09:45:07AM -0400, Tom Talpey wrote:
>> When loading the siw module, ib_uverbs is needed so that consumers may
>> access it. However, siw references only inline functions in ib_uverbs.h,
>> so the kernel linker can not detect this, and the module is not loaded
>> automatically. Add a module dependency to ensure ib_uverbs is present.
> 
> No, that is not how things work.
> 
> Modern rdma-core will auto-load uverbs when something uses it, we
> shouldn't have things like this.

But, it doesn't, for the reason stated - siw only consumes
inline functions from ib_uverbs.h, and the kernel linker has
no clue.

You can test it easily, just load siw on a laptop without any
other RDMA provider. The ib_uverbs module will not be loaded,
and the siw provider won't be seen, rping -s will run but peers
cannot connect for example.

My workaround has been to add a modprobe.d file, but it's a
hack and very non-obvious. Is there a simpler way to allow
ib_uverbs to be auto-loaded for siw?

Tom.