IB/core: Add ib_find_exact_cached_pkey()

When P_Key tables potentially contain both full and partial membership
copies for the same P_Key, we need a function to find the index for an
exact (16-bit) P_Key.

This is necessary when the master forwards QP1 MADs sent by guests.
If the guest has sent the MAD with a limited membership P_Key, we need
to to forward the MAD using the same limited membership P_Key.  Since
the master may have both the limited and the full member P_Keys in its
table, we must make sure to retrieve the limited membership P_Key in
this case.
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/core/cache.c

@@ -199,6 +199,38 @@ int ib_find_cached_pkey(struct ib_device *device,
 }
 EXPORT_SYMBOL(ib_find_cached_pkey);
 
+int ib_find_exact_cached_pkey(struct ib_device *device,
+			      u8                port_num,
+			      u16               pkey,
+			      u16              *index)
+{
+	struct ib_pkey_cache *cache;
+	unsigned long flags;
+	int i;
+	int ret = -ENOENT;
+
+	if (port_num < start_port(device) || port_num > end_port(device))
+		return -EINVAL;
+
+	read_lock_irqsave(&device->cache.lock, flags);
+
+	cache = device->cache.pkey_cache[port_num - start_port(device)];
+
+	*index = -1;
+
+	for (i = 0; i < cache->table_len; ++i)
+		if (cache->table[i] == pkey) {
+			*index = i;
+			ret = 0;
+			break;
+		}
+
+	read_unlock_irqrestore(&device->cache.lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(ib_find_exact_cached_pkey);
+
 int ib_get_cached_lmc(struct ib_device *device,
 		      u8                port_num,
 		      u8                *lmc)

include/rdma/ib_cache.h

@@ -100,6 +100,22 @@ int ib_find_cached_pkey(struct ib_device    *device,
 			u16                  pkey,
 			u16                 *index);
 
+/**
+ * ib_find_exact_cached_pkey - Returns the PKey table index where a specified
+ *   PKey value occurs. Comparison uses the FULL 16 bits (incl membership bit)
+ * @device: The device to query.
+ * @port_num: The port number of the device to search for the PKey.
+ * @pkey: The PKey value to search for.
+ * @index: The index into the cached PKey table where the PKey was found.
+ *
+ * ib_find_exact_cached_pkey() searches the specified PKey table in
+ * the local software cache.
+ */
+int ib_find_exact_cached_pkey(struct ib_device    *device,
+			      u8                   port_num,
+			      u16                  pkey,
+			      u16                 *index);
+
 /**
  * ib_get_cached_lmc - Returns a cached lmc table entry
  * @device: The device to query.