IB/core: Add arbitrary sg_list support

Devices that are capable in registering SG lists
with gaps can now expose it in the core to ULPs
using a new device capability IB_DEVICE_SG_GAPS_REG
(in a new field device_cap_flags_ex in the device attributes
as we ran out of bits), and a new mr_type IB_MR_TYPE_SG_GAPS_REG
which allocates a memory region which is capable of handling
SG lists with gaps.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/verbs.c

@@ -1567,6 +1567,8 @@ EXPORT_SYMBOL(ib_check_mr_status);
  * - The last sg element is allowed to have length less than page_size.
  * - If sg_nents total byte length exceeds the mr max_num_sge * page_size
  *   then only max_num_sg entries will be mapped.
+ * - If the MR was allocated with type IB_MR_TYPE_SG_GAPS_REG, non of these
+ *   constraints holds and the page_size argument is ignored.
  *
  * Returns the number of sg elements that were mapped to the memory region.
  *

include/rdma/ib_verbs.h

@@ -212,6 +212,7 @@ enum ib_device_cap_flags {
 	IB_DEVICE_MANAGED_FLOW_STEERING		= (1 << 29),
 	IB_DEVICE_SIGNATURE_HANDOVER		= (1 << 30),
 	IB_DEVICE_ON_DEMAND_PAGING		= (1 << 31),
+	IB_DEVICE_SG_GAPS_REG			= (1ULL << 32),
 };
 
 enum ib_signature_prot_cap {
@@ -662,10 +663,15 @@ __attribute_const__ int ib_rate_to_mbps(enum ib_rate rate);
  * @IB_MR_TYPE_SIGNATURE:     memory region that is used for
  *                            signature operations (data-integrity
  *                            capable regions)
+ * @IB_MR_TYPE_SG_GAPS:       memory region that is capable to
+ *                            register any arbitrary sg lists (without
+ *                            the normal mr constraints - see
+ *                            ib_map_mr_sg)
  */
 enum ib_mr_type {
 	IB_MR_TYPE_MEM_REG,
 	IB_MR_TYPE_SIGNATURE,
+	IB_MR_TYPE_SG_GAPS,
 };
 
 /**