RDMA/ucma: Add option to manually set IB path

Export rdma_set_ib_paths to user space to allow applications to
manually set the IB path used for connections.  This allows
alternative ways for a user space application or library to obtain
path record information, including retrieving path information
from cached data, avoiding direct interaction with the IB SA.
The IB SA is a single, centralized entity that can limit scaling
on large clusters running MPI applications.

Future changes to the rdma cm can expand on this framework to
support the full range of features allowed by the IB CM, such as
separate forward and reverse paths and APM.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Reviewed-By: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

3 files changed, 26 insertions, 2 deletions

diff --git a/include/rdma/ib_sa.h b/include/rdma/ib_sa.h
index 3841c1aff69..1082afaed15 100644
--- a/include/rdma/ib_sa.h
+++ b/include/rdma/ib_sa.h
@@ -379,4 +379,10 @@ int ib_init_ah_from_path(struct ib_device *device, u8 port_num,
                          struct ib_sa_path_rec *rec,
                          struct ib_ah_attr *ah_attr);
 
+/**
+ * ib_sa_unpack_path - Convert a path record from MAD format to struct
+ * ib_sa_path_rec.
+ */
+void ib_sa_unpack_path(void *attribute, struct ib_sa_path_rec *rec);
+
 #endif /* IB_SA_H */
diff --git a/include/rdma/ib_user_sa.h b/include/rdma/ib_user_sa.h
index 659120157e1..cfc7c9ba781 100644
--- a/include/rdma/ib_user_sa.h
+++ b/include/rdma/ib_user_sa.h
@@ -35,6 +35,22 @@
 
 #include <linux/types.h>
 
+enum {
+        IB_PATH_GMP             = 1,
+        IB_PATH_PRIMARY         = (1<<1),
+        IB_PATH_ALTERNATE       = (1<<2),
+        IB_PATH_OUTBOUND        = (1<<3),
+        IB_PATH_INBOUND         = (1<<4),
+        IB_PATH_INBOUND_REVERSE = (1<<5),
+        IB_PATH_BIDIRECTIONAL   = IB_PATH_OUTBOUND | IB_PATH_INBOUND_REVERSE
+};
+
+struct ib_path_rec_data {
+        __u32   flags;
+        __u32   reserved;
+        __u32   path_rec[16];
+};
+
 struct ib_user_path_rec {
         __u8    dgid[16];
         __u8    sgid[16];
diff --git a/include/rdma/rdma_user_cm.h b/include/rdma/rdma_user_cm.h
index c55705460b8..1d165022c02 100644
--- a/include/rdma/rdma_user_cm.h
+++ b/include/rdma/rdma_user_cm.h
@@ -215,12 +215,14 @@ struct rdma_ucm_event_resp {
 
 /* Option levels */
 enum {
-        RDMA_OPTION_ID          = 0
+        RDMA_OPTION_ID          = 0,
+        RDMA_OPTION_IB          = 1
 };
 
 /* Option details */
 enum {
-        RDMA_OPTION_ID_TOS      = 0
+        RDMA_OPTION_ID_TOS      = 0,
+        RDMA_OPTION_IB_PATH     = 1
 };
 
 struct rdma_ucm_set_option {