Fix wqe_to_link() to use a structure field that we know is definitely
always unused for receive work requests, so that it really avoids the
free list corruption bug that the comment claims it does.
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

Check the sizes of CQs, QPs and SRQs when creating objects, and fail
instead of creating too-big queues.  Also return real limits instead
of just plausible-sounding values from mthca_query_device().
Signed-off-by: NJack Morgenstein <jackm@mellanox.co.il>
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

The hardware relies on us keeping one extra work request that never
gets used in SRQs.  Add checks to the SRQ work request posting
functions so that they fail when someone is about to use up that extra
work request, rather than when someone uses the very last work request.
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

Our hardware supports generating an event when the number of receives
posted to a shared receive queue (SRQ) falls below a user-specified
limit.  Implement mthca_modify_srq() to arm the limit, and add code to
handle dispatching SRQ events when they occur.
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

Userspace SRQs don't have a buffer allocated for them in the kernel, so
it doesn't make sense to set srq->last during initialization.  In fact,
this can crash trying to follow a nonexistent buffer pointer.
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

The error handling paths in mthca_tavor_post_srq_recv() and
mthca_arbel_post_srq_recv() are quite bogus, the result of a
screwed up merge.  Fix them so they work as intended.

Pointed out by Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

Fix posting first WQE for mem-free HCAs: we need to link to previous
WQE even in that case.  While we're at it, simplify code for
Tavor-mode HCAs.  We don't really need the conditional test there
either; we can similarly always link to the previous WQE.

Based on Michael S. Tsirkin's analogous fix for userspace libmthca.
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

Add mthca support for shared receive queues (SRQs),
including userspace SRQs.
Signed-off-by: NRoland Dreier <rolandd@cisco.com>