[IB] Fix MAD layer DMA mappings to avoid touching data buffer once mapped

The MAD layer was violating the DMA API by touching data buffers used
for sends after the DMA mapping was done.  This causes problems on
non-cache-coherent architectures, because the device doing DMA won't
see updates to the payload buffers that exist only in the CPU cache.

Fix this by having all MAD consumers use ib_create_send_mad() to
allocate their send buffers, and moving the DMA mapping into the MAD
layer so it can be done just before calling send (and after any
modifications of the send buffer by the MAD layer).

Tested on a non-cache-coherent PowerPC 440SPe system.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

2 files changed, 34 insertions, 35 deletions

diff --git a/include/rdma/ib_mad.h b/include/rdma/ib_mad.h
index 4172e68..2c13350 100644
--- a/include/rdma/ib_mad.h
+++ b/include/rdma/ib_mad.h
@@ -109,10 +109,14 @@
 #define IB_QP_SET_QKEY	0x80000000
 
 enum {
+	IB_MGMT_MAD_HDR = 24,
 	IB_MGMT_MAD_DATA = 232,
+	IB_MGMT_RMPP_HDR = 36,
 	IB_MGMT_RMPP_DATA = 220,
+	IB_MGMT_VENDOR_HDR = 40,
 	IB_MGMT_VENDOR_DATA = 216,
-	IB_MGMT_SA_DATA = 200
+	IB_MGMT_SA_HDR = 56,
+	IB_MGMT_SA_DATA = 200,
 };
 
 struct ib_mad_hdr {
@@ -203,26 +207,25 @@ struct ib_class_port_info
 
 /**
  * ib_mad_send_buf - MAD data buffer and work request for sends.
- * @mad: References an allocated MAD data buffer.  The size of the data
- *   buffer is specified in the @send_wr.length field.
- * @mapping: DMA mapping information.
+ * @next: A pointer used to chain together MADs for posting.
+ * @mad: References an allocated MAD data buffer.
  * @mad_agent: MAD agent that allocated the buffer.
+ * @ah: The address handle to use when sending the MAD.
  * @context: User-controlled context fields.
- * @send_wr: An initialized work request structure used when sending the MAD.
- *   The wr_id field of the work request is initialized to reference this
- *   data structure.
- * @sge: A scatter-gather list referenced by the work request.
+ * @timeout_ms: Time to wait for a response.
+ * @retries: Number of times to retry a request for a response.
  *
  * Users are responsible for initializing the MAD buffer itself, with the
  * exception of specifying the payload length field in any RMPP MAD.
  */
 struct ib_mad_send_buf {
-	struct ib_mad		*mad;
-	DECLARE_PCI_UNMAP_ADDR(mapping)
+	struct ib_mad_send_buf	*next;
+	void			*mad;
 	struct ib_mad_agent	*mad_agent;
+	struct ib_ah		*ah;
 	void			*context[2];
-	struct ib_send_wr	send_wr;
-	struct ib_sge		sge;
+	int			timeout_ms;
+	int			retries;
 };
 
 /**
@@ -287,7 +290,7 @@ typedef void (*ib_mad_send_handler)(struct ib_mad_agent *mad_agent,
  * or @mad_send_wc.
  */
 typedef void (*ib_mad_snoop_handler)(struct ib_mad_agent *mad_agent,
-				     struct ib_send_wr *send_wr,
+				     struct ib_mad_send_buf *send_buf,
 				     struct ib_mad_send_wc *mad_send_wc);
 
 /**
@@ -334,13 +337,13 @@ struct ib_mad_agent {
 
 /**
  * ib_mad_send_wc - MAD send completion information.
- * @wr_id: Work request identifier associated with the send MAD request.
+ * @send_buf: Send MAD data buffer associated with the send MAD request.
  * @status: Completion status.
  * @vendor_err: Optional vendor error information returned with a failed
  *   request.
  */
 struct ib_mad_send_wc {
-	u64			wr_id;
+	struct ib_mad_send_buf	*send_buf;
 	enum ib_wc_status	status;
 	u32			vendor_err;
 };
@@ -366,7 +369,7 @@ struct ib_mad_recv_buf {
  * @rmpp_list: Specifies a list of RMPP reassembled received MAD buffers.
  * @mad_len: The length of the received MAD, without duplicated headers.
  *
- * For received response, the wr_id field of the wc is set to the wr_id
+ * For received response, the wr_id contains a pointer to the ib_mad_send_buf
  *   for the corresponding send request.
  */
 struct ib_mad_recv_wc {
@@ -463,9 +466,9 @@ int ib_unregister_mad_agent(struct ib_mad_agent *mad_agent);
 /**
  * ib_post_send_mad - Posts MAD(s) to the send queue of the QP associated
  *   with the registered client.
- * @mad_agent: Specifies the associated registration to post the send to.
- * @send_wr: Specifies the information needed to send the MAD(s).
- * @bad_send_wr: Specifies the MAD on which an error was encountered.
+ * @send_buf: Specifies the information needed to send the MAD(s).
+ * @bad_send_buf: Specifies the MAD on which an error was encountered.  This
+ *   parameter is optional if only a single MAD is posted.
  *
  * Sent MADs are not guaranteed to complete in the order that they were posted.
  *
@@ -479,9 +482,8 @@ int ib_unregister_mad_agent(struct ib_mad_agent *mad_agent);
  * defined data being transferred.  The paylen_newwin field should be
  * specified in network-byte order.
  */
-int ib_post_send_mad(struct ib_mad_agent *mad_agent,
-		     struct ib_send_wr *send_wr,
-		     struct ib_send_wr **bad_send_wr);
+int ib_post_send_mad(struct ib_mad_send_buf *send_buf,
+		     struct ib_mad_send_buf **bad_send_buf);
 
 /**
  * ib_coalesce_recv_mad - Coalesces received MAD data into a single buffer.
@@ -507,23 +509,25 @@ void ib_free_recv_mad(struct ib_mad_recv_wc *mad_recv_wc);
 /**
  * ib_cancel_mad - Cancels an outstanding send MAD operation.
  * @mad_agent: Specifies the registration associated with sent MAD.
- * @wr_id: Indicates the work request identifier of the MAD to cancel.
+ * @send_buf: Indicates the MAD to cancel.
  *
  * MADs will be returned to the user through the corresponding
  * ib_mad_send_handler.
  */
-void ib_cancel_mad(struct ib_mad_agent *mad_agent, u64 wr_id);
+void ib_cancel_mad(struct ib_mad_agent *mad_agent,
+		   struct ib_mad_send_buf *send_buf);
 
 /**
  * ib_modify_mad - Modifies an outstanding send MAD operation.
  * @mad_agent: Specifies the registration associated with sent MAD.
- * @wr_id: Indicates the work request identifier of the MAD to modify.
+ * @send_buf: Indicates the MAD to modify.
  * @timeout_ms: New timeout value for sent MAD.
  *
  * This call will reset the timeout value for a sent MAD to the specified
  * value.
  */
-int ib_modify_mad(struct ib_mad_agent *mad_agent, u64 wr_id, u32 timeout_ms);
+int ib_modify_mad(struct ib_mad_agent *mad_agent,
+		  struct ib_mad_send_buf *send_buf, u32 timeout_ms);
 
 /**
  * ib_redirect_mad_qp - Registers a QP for MAD services.
@@ -572,7 +576,6 @@ int ib_process_mad_wc(struct ib_mad_agent *mad_agent,
  * @remote_qpn: Specifies the QPN of the receiving node.
  * @pkey_index: Specifies which PKey the MAD will be sent using.  This field
  *   is valid only if the remote_qpn is QP 1.
- * @ah: References the address handle used to transfer to the remote node.
  * @rmpp_active: Indicates if the send will enable RMPP.
  * @hdr_len: Indicates the size of the data header of the MAD.  This length
  *   should include the common MAD header, RMPP header, plus any class
@@ -582,11 +585,10 @@ int ib_process_mad_wc(struct ib_mad_agent *mad_agent,
  *   additional padding that may be necessary.
  * @gfp_mask: GFP mask used for the memory allocation.
  *
- * This is a helper routine that may be used to allocate a MAD.  Users are
- * not required to allocate outbound MADs using this call.  The returned
- * MAD send buffer will reference a data buffer usable for sending a MAD, along
+ * This routine allocates a MAD for sending.  The returned MAD send buffer
+ * will reference a data buffer usable for sending a MAD, along
  * with an initialized work request structure.  Users may modify the returned
- * MAD data buffer or work request before posting the send.
+ * MAD data buffer before posting the send.
  *
  * The returned data buffer will be cleared.  Users are responsible for
  * initializing the common MAD and any class specific headers.  If @rmpp_active
@@ -594,7 +596,7 @@ int ib_process_mad_wc(struct ib_mad_agent *mad_agent,
  */
 struct ib_mad_send_buf * ib_create_send_mad(struct ib_mad_agent *mad_agent,
 					    u32 remote_qpn, u16 pkey_index,
-					    struct ib_ah *ah, int rmpp_active,
+					    int rmpp_active,
 					    int hdr_len, int data_len,
 					    gfp_t gfp_mask);
 
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index a5a963c..f72d46d 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -595,11 +595,8 @@ struct ib_send_wr {
 		} atomic;
 		struct {
 			struct ib_ah *ah;
-			struct ib_mad_hdr *mad_hdr;
 			u32	remote_qpn;
 			u32	remote_qkey;
-			int	timeout_ms; /* valid for MADs only */
-			int	retries;    /* valid for MADs only */
 			u16	pkey_index; /* valid for GSI only */
 			u8	port_num;   /* valid for DR SMPs on switch only */
 		} ud;