1 files changed, 462 insertions, 0 deletions
diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
new file mode 100644
index 0000000000..13354a1e42
--- /dev/null
+++ b/net/xdp/xsk_queue.h
@@ -0,0 +1,462 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* XDP user-space ring structure
+ * Copyright(c) 2018 Intel Corporation.
+ */
+
+#ifndef _LINUX_XSK_QUEUE_H
+#define _LINUX_XSK_QUEUE_H
+
+#include <linux/types.h>
+#include <linux/if_xdp.h>
+#include <net/xdp_sock.h>
+#include <net/xsk_buff_pool.h>
+
+#include "xsk.h"
+
+struct xdp_ring {
+	u32 producer ____cacheline_aligned_in_smp;
+	/* Hinder the adjacent cache prefetcher to prefetch the consumer
+	 * pointer if the producer pointer is touched and vice versa.
+	 */
+	u32 pad1 ____cacheline_aligned_in_smp;
+	u32 consumer ____cacheline_aligned_in_smp;
+	u32 pad2 ____cacheline_aligned_in_smp;
+	u32 flags;
+	u32 pad3 ____cacheline_aligned_in_smp;
+};
+
+/* Used for the RX and TX queues for packets */
+struct xdp_rxtx_ring {
+	struct xdp_ring ptrs;
+	struct xdp_desc desc[] ____cacheline_aligned_in_smp;
+};
+
+/* Used for the fill and completion queues for buffers */
+struct xdp_umem_ring {
+	struct xdp_ring ptrs;
+	u64 desc[] ____cacheline_aligned_in_smp;
+};
+
+struct xsk_queue {
+	u32 ring_mask;
+	u32 nentries;
+	u32 cached_prod;
+	u32 cached_cons;
+	struct xdp_ring *ring;
+	u64 invalid_descs;
+	u64 queue_empty_descs;
+	size_t ring_vmalloc_size;
+};
+
+struct parsed_desc {
+	u32 mb;
+	u32 valid;
+};
+
+/* The structure of the shared state of the rings are a simple
+ * circular buffer, as outlined in
+ * Documentation/core-api/circular-buffers.rst. For the Rx and
+ * completion ring, the kernel is the producer and user space is the
+ * consumer. For the Tx and fill rings, the kernel is the consumer and
+ * user space is the producer.
+ *
+ * producer                         consumer
+ *
+ * if (LOAD ->consumer) {  (A)      LOAD.acq ->producer  (C)
+ *    STORE $data                   LOAD $data
+ *    STORE.rel ->producer (B)      STORE.rel ->consumer (D)
+ * }
+ *
+ * (A) pairs with (D), and (B) pairs with (C).
+ *
+ * Starting with (B), it protects the data from being written after
+ * the producer pointer. If this barrier was missing, the consumer
+ * could observe the producer pointer being set and thus load the data
+ * before the producer has written the new data. The consumer would in
+ * this case load the old data.
+ *
+ * (C) protects the consumer from speculatively loading the data before
+ * the producer pointer actually has been read. If we do not have this
+ * barrier, some architectures could load old data as speculative loads
+ * are not discarded as the CPU does not know there is a dependency
+ * between ->producer and data.
+ *
+ * (A) is a control dependency that separates the load of ->consumer
+ * from the stores of $data. In case ->consumer indicates there is no
+ * room in the buffer to store $data we do not. The dependency will
+ * order both of the stores after the loads. So no barrier is needed.
+ *
+ * (D) protects the load of the data to be observed to happen after the
+ * store of the consumer pointer. If we did not have this memory
+ * barrier, the producer could observe the consumer pointer being set
+ * and overwrite the data with a new value before the consumer got the
+ * chance to read the old value. The consumer would thus miss reading
+ * the old entry and very likely read the new entry twice, once right
+ * now and again after circling through the ring.
+ */
+
+/* The operations on the rings are the following:
+ *
+ * producer                           consumer
+ *
+ * RESERVE entries                    PEEK in the ring for entries
+ * WRITE data into the ring           READ data from the ring
+ * SUBMIT entries                     RELEASE entries
+ *
+ * The producer reserves one or more entries in the ring. It can then
+ * fill in these entries and finally submit them so that they can be
+ * seen and read by the consumer.
+ *
+ * The consumer peeks into the ring to see if the producer has written
+ * any new entries. If so, the consumer can then read these entries
+ * and when it is done reading them release them back to the producer
+ * so that the producer can use these slots to fill in new entries.
+ *
+ * The function names below reflect these operations.
+ */
+
+/* Functions that read and validate content from consumer rings. */
+
+static inline void __xskq_cons_read_addr_unchecked(struct xsk_queue *q, u32 cached_cons, u64 *addr)
+{
+	struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
+	u32 idx = cached_cons & q->ring_mask;
+
+	*addr = ring->desc[idx];
+}
+
+static inline bool xskq_cons_read_addr_unchecked(struct xsk_queue *q, u64 *addr)
+{
+	if (q->cached_cons != q->cached_prod) {
+		__xskq_cons_read_addr_unchecked(q, q->cached_cons, addr);
+		return true;
+	}
+
+	return false;
+}
+
+static inline bool xp_unused_options_set(u32 options)
+{
+	return options & ~XDP_PKT_CONTD;
+}
+
+static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
+					    struct xdp_desc *desc)
+{
+	u64 offset = desc->addr & (pool->chunk_size - 1);
+
+	if (!desc->len)
+		return false;
+
+	if (offset + desc->len > pool->chunk_size)
+		return false;
+
+	if (desc->addr >= pool->addrs_cnt)
+		return false;
+
+	if (xp_unused_options_set(desc->options))
+		return false;
+	return true;
+}
+
+static inline bool xp_unaligned_validate_desc(struct xsk_buff_pool *pool,
+					      struct xdp_desc *desc)
+{
+	u64 addr = xp_unaligned_add_offset_to_addr(desc->addr);
+
+	if (!desc->len)
+		return false;
+
+	if (desc->len > pool->chunk_size)
+		return false;
+
+	if (addr >= pool->addrs_cnt || addr + desc->len > pool->addrs_cnt ||
+	    xp_desc_crosses_non_contig_pg(pool, addr, desc->len))
+		return false;
+
+	if (xp_unused_options_set(desc->options))
+		return false;
+	return true;
+}
+
+static inline bool xp_validate_desc(struct xsk_buff_pool *pool,
+				    struct xdp_desc *desc)
+{
+	return pool->unaligned ? xp_unaligned_validate_desc(pool, desc) :
+		xp_aligned_validate_desc(pool, desc);
+}
+
+static inline bool xskq_has_descs(struct xsk_queue *q)
+{
+	return q->cached_cons != q->cached_prod;
+}
+
+static inline bool xskq_cons_is_valid_desc(struct xsk_queue *q,
+					   struct xdp_desc *d,
+					   struct xsk_buff_pool *pool)
+{
+	if (!xp_validate_desc(pool, d)) {
+		q->invalid_descs++;
+		return false;
+	}
+	return true;
+}
+
+static inline bool xskq_cons_read_desc(struct xsk_queue *q,
+				       struct xdp_desc *desc,
+				       struct xsk_buff_pool *pool)
+{
+	if (q->cached_cons != q->cached_prod) {
+		struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
+		u32 idx = q->cached_cons & q->ring_mask;
+
+		*desc = ring->desc[idx];
+		return xskq_cons_is_valid_desc(q, desc, pool);
+	}
+
+	q->queue_empty_descs++;
+	return false;
+}
+
+static inline void xskq_cons_release_n(struct xsk_queue *q, u32 cnt)
+{
+	q->cached_cons += cnt;
+}
+
+static inline void parse_desc(struct xsk_queue *q, struct xsk_buff_pool *pool,
+			      struct xdp_desc *desc, struct parsed_desc *parsed)
+{
+	parsed->valid = xskq_cons_is_valid_desc(q, desc, pool);
+	parsed->mb = xp_mb_desc(desc);
+}
+
+static inline
+u32 xskq_cons_read_desc_batch(struct xsk_queue *q, struct xsk_buff_pool *pool,
+			      u32 max)
+{
+	u32 cached_cons = q->cached_cons, nb_entries = 0;
+	struct xdp_desc *descs = pool->tx_descs;
+	u32 total_descs = 0, nr_frags = 0;
+
+	/* track first entry, if stumble upon *any* invalid descriptor, rewind
+	 * current packet that consists of frags and stop the processing
+	 */
+	while (cached_cons != q->cached_prod && nb_entries < max) {
+		struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
+		u32 idx = cached_cons & q->ring_mask;
+		struct parsed_desc parsed;
+
+		descs[nb_entries] = ring->desc[idx];
+		cached_cons++;
+		parse_desc(q, pool, &descs[nb_entries], &parsed);
+		if (unlikely(!parsed.valid))
+			break;
+
+		if (likely(!parsed.mb)) {
+			total_descs += (nr_frags + 1);
+			nr_frags = 0;
+		} else {
+			nr_frags++;
+			if (nr_frags == pool->netdev->xdp_zc_max_segs) {
+				nr_frags = 0;
+				break;
+			}
+		}
+		nb_entries++;
+	}
+
+	cached_cons -= nr_frags;
+	/* Release valid plus any invalid entries */
+	xskq_cons_release_n(q, cached_cons - q->cached_cons);
+	return total_descs;
+}
+
+/* Functions for consumers */
+
+static inline void __xskq_cons_release(struct xsk_queue *q)
+{
+	smp_store_release(&q->ring->consumer, q->cached_cons); /* D, matchees A */
+}
+
+static inline void __xskq_cons_peek(struct xsk_queue *q)
+{
+	/* Refresh the local pointer */
+	q->cached_prod = smp_load_acquire(&q->ring->producer);  /* C, matches B */
+}
+
+static inline void xskq_cons_get_entries(struct xsk_queue *q)
+{
+	__xskq_cons_release(q);
+	__xskq_cons_peek(q);
+}
+
+static inline u32 xskq_cons_nb_entries(struct xsk_queue *q, u32 max)
+{
+	u32 entries = q->cached_prod - q->cached_cons;
+
+	if (entries >= max)
+		return max;
+
+	__xskq_cons_peek(q);
+	entries = q->cached_prod - q->cached_cons;
+
+	return entries >= max ? max : entries;
+}
+
+static inline bool xskq_cons_has_entries(struct xsk_queue *q, u32 cnt)
+{
+	return xskq_cons_nb_entries(q, cnt) >= cnt;
+}
+
+static inline bool xskq_cons_peek_addr_unchecked(struct xsk_queue *q, u64 *addr)
+{
+	if (q->cached_prod == q->cached_cons)
+		xskq_cons_get_entries(q);
+	return xskq_cons_read_addr_unchecked(q, addr);
+}
+
+static inline bool xskq_cons_peek_desc(struct xsk_queue *q,
+				       struct xdp_desc *desc,
+				       struct xsk_buff_pool *pool)
+{
+	if (q->cached_prod == q->cached_cons)
+		xskq_cons_get_entries(q);
+	return xskq_cons_read_desc(q, desc, pool);
+}
+
+/* To improve performance in the xskq_cons_release functions, only update local state here.
+ * Reflect this to global state when we get new entries from the ring in
+ * xskq_cons_get_entries() and whenever Rx or Tx processing are completed in the NAPI loop.
+ */
+static inline void xskq_cons_release(struct xsk_queue *q)
+{
+	q->cached_cons++;
+}
+
+static inline void xskq_cons_cancel_n(struct xsk_queue *q, u32 cnt)
+{
+	q->cached_cons -= cnt;
+}
+
+static inline u32 xskq_cons_present_entries(struct xsk_queue *q)
+{
+	/* No barriers needed since data is not accessed */
+	return READ_ONCE(q->ring->producer) - READ_ONCE(q->ring->consumer);
+}
+
+/* Functions for producers */
+
+static inline u32 xskq_prod_nb_free(struct xsk_queue *q, u32 max)
+{
+	u32 free_entries = q->nentries - (q->cached_prod - q->cached_cons);
+
+	if (free_entries >= max)
+		return max;
+
+	/* Refresh the local tail pointer */
+	q->cached_cons = READ_ONCE(q->ring->consumer);
+	free_entries = q->nentries - (q->cached_prod - q->cached_cons);
+
+	return free_entries >= max ? max : free_entries;
+}
+
+static inline bool xskq_prod_is_full(struct xsk_queue *q)
+{
+	return xskq_prod_nb_free(q, 1) ? false : true;
+}
+
+static inline void xskq_prod_cancel_n(struct xsk_queue *q, u32 cnt)
+{
+	q->cached_prod -= cnt;
+}
+
+static inline int xskq_prod_reserve(struct xsk_queue *q)
+{
+	if (xskq_prod_is_full(q))
+		return -ENOSPC;
+
+	/* A, matches D */
+	q->cached_prod++;
+	return 0;
+}
+
+static inline int xskq_prod_reserve_addr(struct xsk_queue *q, u64 addr)
+{
+	struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
+
+	if (xskq_prod_is_full(q))
+		return -ENOSPC;
+
+	/* A, matches D */
+	ring->desc[q->cached_prod++ & q->ring_mask] = addr;
+	return 0;
+}
+
+static inline void xskq_prod_write_addr_batch(struct xsk_queue *q, struct xdp_desc *descs,
+					      u32 nb_entries)
+{
+	struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
+	u32 i, cached_prod;
+
+	/* A, matches D */
+	cached_prod = q->cached_prod;
+	for (i = 0; i < nb_entries; i++)
+		ring->desc[cached_prod++ & q->ring_mask] = descs[i].addr;
+	q->cached_prod = cached_prod;
+}
+
+static inline int xskq_prod_reserve_desc(struct xsk_queue *q,
+					 u64 addr, u32 len, u32 flags)
+{
+	struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
+	u32 idx;
+
+	if (xskq_prod_is_full(q))
+		return -ENOBUFS;
+
+	/* A, matches D */
+	idx = q->cached_prod++ & q->ring_mask;
+	ring->desc[idx].addr = addr;
+	ring->desc[idx].len = len;
+	ring->desc[idx].options = flags;
+
+	return 0;
+}
+
+static inline void __xskq_prod_submit(struct xsk_queue *q, u32 idx)
+{
+	smp_store_release(&q->ring->producer, idx); /* B, matches C */
+}
+
+static inline void xskq_prod_submit(struct xsk_queue *q)
+{
+	__xskq_prod_submit(q, q->cached_prod);
+}
+
+static inline void xskq_prod_submit_n(struct xsk_queue *q, u32 nb_entries)
+{
+	__xskq_prod_submit(q, q->ring->producer + nb_entries);
+}
+
+static inline bool xskq_prod_is_empty(struct xsk_queue *q)
+{
+	/* No barriers needed since data is not accessed */
+	return READ_ONCE(q->ring->consumer) == READ_ONCE(q->ring->producer);
+}
+
+/* For both producers and consumers */
+
+static inline u64 xskq_nb_invalid_descs(struct xsk_queue *q)
+{
+	return q ? q->invalid_descs : 0;
+}
+
+static inline u64 xskq_nb_queue_empty_descs(struct xsk_queue *q)
+{
+	return q ? q->queue_empty_descs : 0;
+}
+
+struct xsk_queue *xskq_create(u32 nentries, bool umem_queue);
+void xskq_destroy(struct xsk_queue *q_ops);
+
+#endif /* _LINUX_XSK_QUEUE_H */