RDMA/uverbs: Add new relaxed ordering memory region access flag

Add a new relaxed ordering access flag for memory regions.  Using memory
regions with relaxed ordeing set can enhance performance.

This access flag is handled in a best-effort manner, drivers should ignore
if they don't support setting relaxed ordering.

Link: https://lore.kernel.org/r/1578506740-22188-9-git-send-email-yishaih@mellanox.comSigned-off-by: Michael Guralnik <michaelgur@mellanox.com>
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

include/rdma/ib_verbs.h

@@ -1418,6 +1418,7 @@ enum ib_access_flags {
 	IB_ZERO_BASED = IB_UVERBS_ACCESS_ZERO_BASED,
 	IB_ACCESS_ON_DEMAND = IB_UVERBS_ACCESS_ON_DEMAND,
 	IB_ACCESS_HUGETLB = IB_UVERBS_ACCESS_HUGETLB,
+	IB_ACCESS_RELAXED_ORDERING = IB_UVERBS_ACCESS_RELAXED_ORDERING,
 
 	IB_ACCESS_OPTIONAL = IB_UVERBS_ACCESS_OPTIONAL_RANGE,
 	IB_ACCESS_SUPPORTED =

include/uapi/rdma/ib_user_ioctl_verbs.h

@@ -54,6 +54,7 @@ enum ib_uverbs_access_flags {
 	IB_UVERBS_ACCESS_ON_DEMAND = 1 << 6,
 	IB_UVERBS_ACCESS_HUGETLB = 1 << 7,
 
+	IB_UVERBS_ACCESS_RELAXED_ORDERING = IB_UVERBS_ACCESS_OPTIONAL_FIRST,
 	IB_UVERBS_ACCESS_OPTIONAL_RANGE =
 		((IB_UVERBS_ACCESS_OPTIONAL_LAST << 1) - 1) &
 		~(IB_UVERBS_ACCESS_OPTIONAL_FIRST - 1)