[PATCH] mbuf: replace GCC marker extension with C11 anonymous unions

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

Replace the use of RTE_MARKER<x> with C11 anonymous unions to improve
code portability between toolchains.

Update use of rte_mbuf rearm_data field in net/ionic, net/sfc and
net/virtio which were accessing field as a zero-length array.

Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
---
 drivers/net/ionic/ionic_lif.c               |   8 +-
 drivers/net/ionic/ionic_rxtx_sg.c           |   4 +-
 drivers/net/ionic/ionic_rxtx_simple.c       |   2 +-
 drivers/net/sfc/sfc_ef100_rx.c              |   8 +-
 drivers/net/sfc/sfc_ef10_rx.c               |  12 +--
 drivers/net/virtio/virtio_rxtx_packed_avx.h |   8 +-
 lib/mbuf/rte_mbuf_core.h                    | 135 +++++++++++++++-------------
 7 files changed, 94 insertions(+), 83 deletions(-)

diff --git a/drivers/net/ionic/ionic_lif.c b/drivers/net/ionic/ionic_lif.c
index 25b490d..fd99f39 100644
--- a/drivers/net/ionic/ionic_lif.c
+++ b/drivers/net/ionic/ionic_lif.c
@@ -725,8 +725,8 @@
 
 	rte_compiler_barrier();
 
-	RTE_BUILD_BUG_ON(sizeof(rxm.rearm_data[0]) != sizeof(uint64_t));
-	return rxm.rearm_data[0];
+	RTE_BUILD_BUG_ON(sizeof(rxm.rearm_data) != sizeof(uint64_t));
+	return rxm.rearm_data;
 }
 
 static uint64_t
@@ -743,8 +743,8 @@
 
 	rte_compiler_barrier();
 
-	RTE_BUILD_BUG_ON(sizeof(rxm.rearm_data[0]) != sizeof(uint64_t));
-	return rxm.rearm_data[0];
+	RTE_BUILD_BUG_ON(sizeof(rxm.rearm_data) != sizeof(uint64_t));
+	return rxm.rearm_data;
 }
 
 int
diff --git a/drivers/net/ionic/ionic_rxtx_sg.c b/drivers/net/ionic/ionic_rxtx_sg.c
index ab8e56e..a569dd1 100644
--- a/drivers/net/ionic/ionic_rxtx_sg.c
+++ b/drivers/net/ionic/ionic_rxtx_sg.c
@@ -285,7 +285,7 @@
 	info[0] = NULL;
 
 	/* Set the mbuf metadata based on the cq entry */
-	rxm->rearm_data[0] = rxq->rearm_data;
+	rxm->rearm_data = rxq->rearm_data;
 	rxm->pkt_len = cq_desc_len;
 	rxm->data_len = RTE_MIN(rxq->hdr_seg_size, cq_desc_len);
 	left = cq_desc_len - rxm->data_len;
@@ -298,7 +298,7 @@
 		info[i] = NULL;
 
 		/* Set the chained mbuf metadata */
-		rxm_seg->rearm_data[0] = rxq->rearm_seg_data;
+		rxm_seg->rearm_data = rxq->rearm_seg_data;
 		rxm_seg->data_len = RTE_MIN(rxq->seg_size, left);
 		left -= rxm_seg->data_len;
 
diff --git a/drivers/net/ionic/ionic_rxtx_simple.c b/drivers/net/ionic/ionic_rxtx_simple.c
index 5f81856..1978610 100644
--- a/drivers/net/ionic/ionic_rxtx_simple.c
+++ b/drivers/net/ionic/ionic_rxtx_simple.c
@@ -256,7 +256,7 @@
 	info[0] = NULL;
 
 	/* Set the mbuf metadata based on the cq entry */
-	rxm->rearm_data[0] = rxq->rearm_data;
+	rxm->rearm_data = rxq->rearm_data;
 	rxm->pkt_len = cq_desc_len;
 	rxm->data_len = cq_desc_len;
 
diff --git a/drivers/net/sfc/sfc_ef100_rx.c b/drivers/net/sfc/sfc_ef100_rx.c
index 2677003..23918d5 100644
--- a/drivers/net/sfc/sfc_ef100_rx.c
+++ b/drivers/net/sfc/sfc_ef100_rx.c
@@ -553,9 +553,9 @@ struct sfc_ef100_rxq {
 		pkt = sfc_ef100_rx_next_mbuf(rxq);
 		__rte_mbuf_raw_sanity_check(pkt);
 
-		RTE_BUILD_BUG_ON(sizeof(pkt->rearm_data[0]) !=
+		RTE_BUILD_BUG_ON(sizeof(pkt->rearm_data) !=
 				 sizeof(rxq->rearm_data));
-		pkt->rearm_data[0] = rxq->rearm_data;
+		pkt->rearm_data = rxq->rearm_data;
 
 		/* data_off already moved past Rx prefix */
 		rx_prefix = (const efx_xword_t *)sfc_ef100_rx_pkt_prefix(pkt);
@@ -759,8 +759,8 @@ struct sfc_ef100_rxq {
 
 	/* rearm_data covers structure members filled in above */
 	rte_compiler_barrier();
-	RTE_BUILD_BUG_ON(sizeof(m.rearm_data[0]) != sizeof(uint64_t));
-	return m.rearm_data[0];
+	RTE_BUILD_BUG_ON(sizeof(m.rearm_data) != sizeof(uint64_t));
+	return m.rearm_data;
 }
 
 static sfc_dp_rx_qcreate_t sfc_ef100_rx_qcreate;
diff --git a/drivers/net/sfc/sfc_ef10_rx.c b/drivers/net/sfc/sfc_ef10_rx.c
index 30a320d..60bc098 100644
--- a/drivers/net/sfc/sfc_ef10_rx.c
+++ b/drivers/net/sfc/sfc_ef10_rx.c
@@ -322,8 +322,8 @@ struct sfc_ef10_rxq {
 
 	m = rxd->mbuf;
 
-	RTE_BUILD_BUG_ON(sizeof(m->rearm_data[0]) != sizeof(rxq->rearm_data));
-	m->rearm_data[0] = rxq->rearm_data;
+	RTE_BUILD_BUG_ON(sizeof(m->rearm_data) != sizeof(rxq->rearm_data));
+	m->rearm_data = rxq->rearm_data;
 
 	/* Classify packet based on Rx event */
 	/* Mask RSS hash offload flag if RSS is not enabled */
@@ -377,9 +377,9 @@ struct sfc_ef10_rxq {
 			rxq->completed = pending;
 		}
 
-		RTE_BUILD_BUG_ON(sizeof(m->rearm_data[0]) !=
+		RTE_BUILD_BUG_ON(sizeof(m->rearm_data) !=
 				 sizeof(rxq->rearm_data));
-		m->rearm_data[0] = rxq->rearm_data;
+		m->rearm_data = rxq->rearm_data;
 
 		/* Event-dependent information is the same */
 		m->ol_flags = m0->ol_flags;
@@ -633,8 +633,8 @@ struct sfc_ef10_rxq {
 
 	/* rearm_data covers structure members filled in above */
 	rte_compiler_barrier();
-	RTE_BUILD_BUG_ON(sizeof(m.rearm_data[0]) != sizeof(uint64_t));
-	return m.rearm_data[0];
+	RTE_BUILD_BUG_ON(sizeof(m.rearm_data) != sizeof(uint64_t));
+	return m.rearm_data;
 }
 
 static sfc_dp_rx_qcreate_t sfc_ef10_rx_qcreate;
diff --git a/drivers/net/virtio/virtio_rxtx_packed_avx.h b/drivers/net/virtio/virtio_rxtx_packed_avx.h
index 584ac72..a9ce53f 100644
--- a/drivers/net/virtio/virtio_rxtx_packed_avx.h
+++ b/drivers/net/virtio/virtio_rxtx_packed_avx.h
@@ -36,10 +36,10 @@
 	/* Load four mbufs rearm data */
 	RTE_BUILD_BUG_ON(REFCNT_BITS_OFFSET >= 64);
 	RTE_BUILD_BUG_ON(SEG_NUM_BITS_OFFSET >= 64);
-	__m256i mbufs = _mm256_set_epi64x(*tx_pkts[3]->rearm_data,
-					  *tx_pkts[2]->rearm_data,
-					  *tx_pkts[1]->rearm_data,
-					  *tx_pkts[0]->rearm_data);
+	__m256i mbufs = _mm256_set_epi64x(tx_pkts[3]->rearm_data,
+					  tx_pkts[2]->rearm_data,
+					  tx_pkts[1]->rearm_data,
+					  tx_pkts[0]->rearm_data);
 
 	/* refcnt=1 and nb_segs=1 */
 	__m256i mbuf_ref = _mm256_set1_epi64x(DEFAULT_REARM_DATA);
diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h
index 5688683..d731ea0 100644
--- a/lib/mbuf/rte_mbuf_core.h
+++ b/lib/mbuf/rte_mbuf_core.h
@@ -464,9 +464,10 @@ enum {
  * The generic rte_mbuf, containing a packet mbuf.
  */
 struct rte_mbuf {
-	RTE_MARKER cacheline0;
-
-	void *buf_addr;           /**< Virtual address of segment buffer. */
+	union {
+	    void *cacheline0;
+	    void *buf_addr;           /**< Virtual address of segment buffer. */
+	};
 #if RTE_IOVA_IN_MBUF
 	/**
 	 * Physical address of segment buffer.
@@ -487,69 +488,77 @@ struct rte_mbuf {
 #endif
 
 	/* next 8 bytes are initialised on RX descriptor rearm */
-	RTE_MARKER64 rearm_data;
-	uint16_t data_off;
-
-	/**
-	 * Reference counter. Its size should at least equal to the size
-	 * of port field (16 bits), to support zero-copy broadcast.
-	 * It should only be accessed using the following functions:
-	 * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(), and
-	 * rte_mbuf_refcnt_set(). The functionality of these functions (atomic,
-	 * or non-atomic) is controlled by the RTE_MBUF_REFCNT_ATOMIC flag.
-	 */
-	RTE_ATOMIC(uint16_t) refcnt;
+	union {
+		uint64_t rearm_data;
+		struct {
+			uint16_t data_off;
+
+			/**
+			 * Reference counter. Its size should at least equal to the size
+			 * of port field (16 bits), to support zero-copy broadcast.
+			 * It should only be accessed using the following functions:
+			 * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(), and
+			 * rte_mbuf_refcnt_set(). The functionality of these functions (atomic,
+			 * or non-atomic) is controlled by the RTE_MBUF_REFCNT_ATOMIC flag.
+			 */
+			RTE_ATOMIC(uint16_t) refcnt;
 
-	/**
-	 * Number of segments. Only valid for the first segment of an mbuf
-	 * chain.
-	 */
-	uint16_t nb_segs;
+			/**
+			 * Number of segments. Only valid for the first segment of an mbuf
+			 * chain.
+			 */
+			uint16_t nb_segs;
 
-	/** Input port (16 bits to support more than 256 virtual ports).
-	 * The event eth Tx adapter uses this field to specify the output port.
-	 */
-	uint16_t port;
+			/** Input port (16 bits to support more than 256 virtual ports).
+			 * The event eth Tx adapter uses this field to specify the output port.
+			 */
+			uint16_t port;
 
-	uint64_t ol_flags;        /**< Offload features. */
+			uint64_t ol_flags;        /**< Offload features. */
+		};
+	};
 
 	/* remaining bytes are set on RX when pulling packet from descriptor */
-	RTE_MARKER rx_descriptor_fields1;
-
-	/*
-	 * The packet type, which is the combination of outer/inner L2, L3, L4
-	 * and tunnel types. The packet_type is about data really present in the
-	 * mbuf. Example: if vlan stripping is enabled, a received vlan packet
-	 * would have RTE_PTYPE_L2_ETHER and not RTE_PTYPE_L2_VLAN because the
-	 * vlan is stripped from the data.
-	 */
 	union {
-		uint32_t packet_type; /**< L2/L3/L4 and tunnel information. */
-		__extension__
+		void *rx_descriptor_fields1;
+
+		/*
+		 * The packet type, which is the combination of outer/inner L2, L3, L4
+		 * and tunnel types. The packet_type is about data really present in the
+		 * mbuf. Example: if vlan stripping is enabled, a received vlan packet
+		 * would have RTE_PTYPE_L2_ETHER and not RTE_PTYPE_L2_VLAN because the
+		 * vlan is stripped from the data.
+		 */
 		struct {
-			uint8_t l2_type:4;   /**< (Outer) L2 type. */
-			uint8_t l3_type:4;   /**< (Outer) L3 type. */
-			uint8_t l4_type:4;   /**< (Outer) L4 type. */
-			uint8_t tun_type:4;  /**< Tunnel type. */
 			union {
-				uint8_t inner_esp_next_proto;
-				/**< ESP next protocol type, valid if
-				 * RTE_PTYPE_TUNNEL_ESP tunnel type is set
-				 * on both Tx and Rx.
-				 */
+				uint32_t packet_type; /**< L2/L3/L4 and tunnel information. */
 				__extension__
 				struct {
-					uint8_t inner_l2_type:4;
-					/**< Inner L2 type. */
-					uint8_t inner_l3_type:4;
-					/**< Inner L3 type. */
+					uint8_t l2_type:4;   /**< (Outer) L2 type. */
+					uint8_t l3_type:4;   /**< (Outer) L3 type. */
+					uint8_t l4_type:4;   /**< (Outer) L4 type. */
+					uint8_t tun_type:4;  /**< Tunnel type. */
+					union {
+						uint8_t inner_esp_next_proto;
+						/**< ESP next protocol type, valid if
+						 * RTE_PTYPE_TUNNEL_ESP tunnel type is set
+						 * on both Tx and Rx.
+						 */
+						__extension__
+						struct {
+							uint8_t inner_l2_type:4;
+							/**< Inner L2 type. */
+							uint8_t inner_l3_type:4;
+							/**< Inner L3 type. */
+						};
+					};
+					uint8_t inner_l4_type:4; /**< Inner L4 type. */
 				};
 			};
-			uint8_t inner_l4_type:4; /**< Inner L4 type. */
+			uint32_t pkt_len;         /**< Total pkt len: sum of all segments. */
 		};
 	};
 
-	uint32_t pkt_len;         /**< Total pkt len: sum of all segments. */
 	uint16_t data_len;        /**< Amount of data in segment buffer. */
 	/** VLAN TCI (CPU order), valid if RTE_MBUF_F_RX_VLAN is set. */
 	uint16_t vlan_tci;
@@ -595,21 +604,23 @@ struct rte_mbuf {
 	struct rte_mempool *pool; /**< Pool from which mbuf was allocated. */
 
 	/* second cache line - fields only used in slow path or on TX */
-	RTE_MARKER cacheline1 __rte_cache_min_aligned;
+	union {
+		void *cacheline1;
 
 #if RTE_IOVA_IN_MBUF
-	/**
-	 * Next segment of scattered packet. Must be NULL in the last
-	 * segment or in case of non-segmented packet.
-	 */
-	struct rte_mbuf *next;
+		/**
+		 * Next segment of scattered packet. Must be NULL in the last
+		 * segment or in case of non-segmented packet.
+		 */
+		struct rte_mbuf *next;
 #else
-	/**
-	 * Reserved for dynamic fields
-	 * when the next pointer is in first cache line (i.e. RTE_IOVA_IN_MBUF is 0).
-	 */
-	uint64_t dynfield2;
+		/**
+		 * Reserved for dynamic fields
+		 * when the next pointer is in first cache line (i.e. RTE_IOVA_IN_MBUF is 0).
+		 */
+		uint64_t dynfield2;
 #endif
+	};
 
 	/* fields to support TX offloads */
 	union {
-- 
1.8.3.1