prov/efa: Improve efa_rdm_pke definition

This removes the hardcoded padding bytes from the struct definition,
which were ostensibly used as a mechanism to enforce alignment of
wiredata to the 128 byte boundary.

While the static_asserts somewhat protect against changes made to the
members which the struct is composed of, the manual calculation is a
maintenance headache which is prone to developer error, as well as
implementation-defined quirks.

More importantly, this change more clearly indicates the intent to
align to the 128-byte boundary.

This commit also makes the struct size uniform when debug mode is
enabled. This wasn't (currently) necessary, as the 32 bytes of padding
were already sufficient for the 16-byte dlist_entry struct.

This is the C11-compliant version, utilizing _Alignas (stdalign.h)

Signed-off-by: Darryl Abbate <drl@amazon.com>

prov/efa/src/rdm/efa_rdm_pke.h

@@ -1,49 +1,21 @@
-/*
- * Copyright (c) Amazon.com, Inc. or its affiliates.
- * All rights reserved.
- *
- * This software is available to you under a choice of one of two
- * licenses.  You may choose to be licensed under the terms of the GNU
- * General Public License (GPL) Version 2, available from the file
- * COPYING in the main directory of this source tree, or the
- * BSD license below:
- *
- *     Redistribution and use in source and binary forms, with or
- *     without modification, are permitted provided that the following
- *     conditions are met:
- *
- *      - Redistributions of source code must retain the above
- *        copyright notice, this list of conditions and the following
- *        disclaimer.
- *
- *      - Redistributions in binary form must reproduce the above
- *        copyright notice, this list of conditions and the following
- *        disclaimer in the documentation and/or other materials
- *        provided with the distribution.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
- * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
- * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
- * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
- * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
- * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
- * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
+/* Copyright Amazon.com, Inc. or its affiliates. All rights reserved. */
+/* SPDX-License-Identifier: BSD-2-Clause OR GPL-2.0-only */
 
 #ifndef _EFA_RDM_PKE_H
 #define _EFA_RDM_PKE_H
 
+#include <stdalign.h>
 #include <uthash.h>
 #include <ofi_mem.h>
 #include <ofi_list.h>
 
 #define EFA_RDM_PKE_IN_USE		BIT_ULL(0) /**< this packet entry is being used */
 #define EFA_RDM_PKE_RNR_RETRANSMIT	BIT_ULL(1) /**< this packet entry encountered RNR and is being retransmitted*/
-#define EFA_RDM_PKE_LOCAL_READ	BIT_ULL(2) /**< this packet entry is used as context of a local read operation */
+#define EFA_RDM_PKE_LOCAL_READ		BIT_ULL(2) /**< this packet entry is used as context of a local read operation */
 #define EFA_RDM_PKE_DC_LONGCTS_DATA	BIT_ULL(3) /**< this DATA packet entry is used by a delivery complete LONGCTS send/write protocol*/
-#define EFA_RDM_PKE_LOCAL_WRITE	BIT_ULL(4) /**< this packet entry is used as context of an RDMA Write to self */
+#define EFA_RDM_PKE_LOCAL_WRITE		BIT_ULL(4) /**< this packet entry is used as context of an RDMA Write to self */
 
+#define EFA_RDM_PKE_ALIGNMENT		128
 
 /**
  * @enum for packet entry allocation type
@@ -111,7 +83,6 @@ struct efa_rdm_pke {
 #if ENABLE_DEBUG
 	/** @brief entry to a linked list of posted buf list */
 	struct dlist_entry dbg_entry;
-	uint8_t pad[112];
 #endif
 	/** @brief pointer to #efa_rdm_ep */
 	struct efa_rdm_ep *ep;
@@ -203,8 +174,6 @@ struct efa_rdm_pke {
 	 */
 	size_t payload_size;
 
-	uint8_t pad2[32];
-
 	/** @brief buffer that contains data that is going over wire
 	 *
 	 * @details
@@ -222,15 +191,11 @@ struct efa_rdm_pke {
 	 *       (thus data has been copied to wiredata).
 	 *    b) packet is an incoming (RX) packet.
 	 */
-	char wiredata[0];
+	_Alignas(EFA_RDM_PKE_ALIGNMENT) char wiredata[0];
 };
 
 #if defined(static_assert) && defined(__x86_64__)
-#if ENABLE_DEBUG
-static_assert(sizeof(struct efa_rdm_pke) == 256, "efa_rdm_pke check");
-#else
-static_assert(sizeof(struct efa_rdm_pke) == 128, "efa_rdm_pke check");
-#endif
+static_assert(sizeof (struct efa_rdm_pke) % EFA_RDM_PKE_ALIGNMENT == 0, "efa_rdm_pke alignment check");
 #endif
 
 struct efa_rdm_ep;