I'm testing MOFED 5.1 Beta candidate with lustre master. And I got the following compilation error:
Type 'make' to build Lustre.
+ grep -q 'define[[:space:]]*HAVE_SERVER_SUPPORT' config.h
+ make -j24 -s
Making all in .
/tmp/rpmbuild-lustre--ToFAMKNQ/BUILD/lustre-2.13.54_148_g3fcceea/lnet/klnds/o2iblnd/o2iblnd_cb.c: In function 'kiblnd_reject':
/tmp/rpmbuild-lustre--ToFAMKNQ/BUILD/lustre-2.13.54_148_g3fcceea/lnet/klnds/o2iblnd/o2iblnd_cb.c:2296:9: error: too few arguments to function 'rdma_reject'
rc = rdma_reject(cmid, rej, sizeof(*rej));
The error is related to a change in RDMA_CM API. The change came to MOFED from the upstream kernel:

commit 8094ba0ace7f6cd1e31ea8b151fba3594cadfa9a
Author: Leon Romanovsky <leonro@mellanox.com>
Date: Tue May 26 13:33:04 2020 +0300
RDMA/cma: Provide ECE reject reason
IBTA declares "vendor option not supported" reject reason in REJ messages
 if passive side doesn't want to accept proposed ECE options.
Due to the fact that ECE is managed by userspace, there is a need to let
 users to provide such rejected reason.
Link: https://lore.kernel.org/r/20200526103304.196371-7-leon@kernel.org
 Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
 Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

And the same error is expected with kernel 5.8.

I have a patch for the lustre to support MOFED 5.1 and kernel 5.8. I will push the patch for review soon.