[PATCH v2 03/10] xsk: add support to allow unaligned chunk placement

[Kevin Laatz <kevin.laatz@intel.com>]

Currently, addresses are chunk size aligned. This means, we are very
restricted in terms of where we can place chunk within the umem. For
example, if we have a chunk size of 2k, then our chunks can only be placed
at 0,2k,4k,6k,8k... and so on (ie. every 2k starting from 0).

This patch introduces the ability to use unaligned chunks. With these
changes, we are no longer bound to having to place chunks at a 2k (or
whatever your chunk size is) interval. Since we are no longer dealing with
aligned chunks, they can now cross page boundaries. Checks for page
contiguity have been added in order to keep track of which pages are
followed by a physically contiguous page.

Signed-off-by: Kevin Laatz <kevin.laatz@intel.com>
Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>

---
v2:
  - Add checks for the flags coming from userspace
  - Fix how we get chunk_size in xsk_diag.c
  - Add defines for masking the new descriptor format
  - Modified the rx functions to use new descriptor format
  - Modified the tx functions to use new descriptor format
---
 include/net/xdp_sock.h      |  2 +
 include/uapi/linux/if_xdp.h |  9 ++++
 net/xdp/xdp_umem.c          | 17 ++++---
 net/xdp/xsk.c               | 89 ++++++++++++++++++++++++++++++-------
 net/xdp/xsk_diag.c          |  2 +-
 net/xdp/xsk_queue.h         | 70 +++++++++++++++++++++++++----
 6 files changed, 159 insertions(+), 30 deletions(-)

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index 69796d264f06..f7ab8ff33f06 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -19,6 +19,7 @@ struct xsk_queue;
 struct xdp_umem_page {
 	void *addr;
 	dma_addr_t dma;
+	bool next_pg_contig;
 };
 
 struct xdp_umem_fq_reuse {
@@ -48,6 +49,7 @@ struct xdp_umem {
 	bool zc;
 	spinlock_t xsk_list_lock;
 	struct list_head xsk_list;
+	u32 flags;
 };
 
 struct xdp_sock {
diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
index faaa5ca2a117..f8dc68fcdf78 100644
--- a/include/uapi/linux/if_xdp.h
+++ b/include/uapi/linux/if_xdp.h
@@ -17,6 +17,9 @@
 #define XDP_COPY	(1 << 1) /* Force copy-mode */
 #define XDP_ZEROCOPY	(1 << 2) /* Force zero-copy mode */
 
+/* Flags for xsk_umem_config flags */
+#define XDP_UMEM_UNALIGNED_CHUNKS (1 << 0)
+
 struct sockaddr_xdp {
 	__u16 sxdp_family;
 	__u16 sxdp_flags;
@@ -53,6 +56,7 @@ struct xdp_umem_reg {
 	__u64 len; /* Length of packet data area */
 	__u32 chunk_size;
 	__u32 headroom;
+	__u32 flags;
 };
 
 struct xdp_statistics {
@@ -74,6 +78,11 @@ struct xdp_options {
 #define XDP_UMEM_PGOFF_FILL_RING	0x100000000ULL
 #define XDP_UMEM_PGOFF_COMPLETION_RING	0x180000000ULL
 
+/* Masks for unaligned chunks mode */
+#define XSK_UNALIGNED_BUF_OFFSET_SHIFT 48
+#define XSK_UNALIGNED_BUF_ADDR_MASK \
+	((1ULL << XSK_UNALIGNED_BUF_OFFSET_SHIFT) - 1)
+
 /* Rx/Tx descriptor */
 struct xdp_desc {
 	__u64 addr;
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 20c91f02d3d8..6130735bdd3d 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -303,6 +303,7 @@ static int xdp_umem_account_pages(struct xdp_umem *umem)
 
 static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 {
+	bool unaligned_chunks = mr->flags & XDP_UMEM_UNALIGNED_CHUNKS;
 	u32 chunk_size = mr->chunk_size, headroom = mr->headroom;
 	unsigned int chunks, chunks_per_page;
 	u64 addr = mr->addr, size = mr->len;
@@ -318,7 +319,10 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 		return -EINVAL;
 	}
 
-	if (!is_power_of_2(chunk_size))
+	if (mr->flags & ~(XDP_UMEM_UNALIGNED_CHUNKS))
+		return -EINVAL;
+
+	if (!unaligned_chunks && !is_power_of_2(chunk_size))
 		return -EINVAL;
 
 	if (!PAGE_ALIGNED(addr)) {
@@ -335,9 +339,11 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	if (chunks == 0)
 		return -EINVAL;
 
-	chunks_per_page = PAGE_SIZE / chunk_size;
-	if (chunks < chunks_per_page || chunks % chunks_per_page)
-		return -EINVAL;
+	if (!unaligned_chunks) {
+		chunks_per_page = PAGE_SIZE / chunk_size;
+		if (chunks < chunks_per_page || chunks % chunks_per_page)
+			return -EINVAL;
+	}
 
 	headroom = ALIGN(headroom, 64);
 
@@ -346,13 +352,14 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 		return -EINVAL;
 
 	umem->address = (unsigned long)addr;
-	umem->chunk_mask = ~((u64)chunk_size - 1);
+	umem->chunk_mask = unaligned_chunks ? U64_MAX : ~((u64)chunk_size - 1);
 	umem->size = size;
 	umem->headroom = headroom;
 	umem->chunk_size_nohr = chunk_size - headroom;
 	umem->npgs = size / PAGE_SIZE;
 	umem->pgs = NULL;
 	umem->user = NULL;
+	umem->flags = mr->flags;
 	INIT_LIST_HEAD(&umem->xsk_list);
 	spin_lock_init(&umem->xsk_list_lock);
 
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index d4d6f10aa936..78089825821a 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -45,7 +45,7 @@ EXPORT_SYMBOL(xsk_umem_has_addrs);
 
 u64 *xsk_umem_peek_addr(struct xdp_umem *umem, u64 *addr)
 {
-	return xskq_peek_addr(umem->fq, addr);
+	return xskq_peek_addr(umem->fq, addr, umem);
 }
 EXPORT_SYMBOL(xsk_umem_peek_addr);
 
@@ -55,21 +55,42 @@ void xsk_umem_discard_addr(struct xdp_umem *umem)
 }
 EXPORT_SYMBOL(xsk_umem_discard_addr);
 
+/* If a buffer crosses a page boundary, we need to do 2 memcpy's, one for
+ * each page. This is only required in copy mode.
+ */
+static void __xsk_rcv_memcpy(struct xdp_umem *umem, u64 addr, void *from_buf,
+			     u32 len, u32 metalen)
+{
+	void *to_buf = xdp_umem_get_data(umem, addr);
+
+	if (xskq_crosses_non_contig_pg(umem, addr, len + metalen)) {
+		void *next_pg_addr = umem->pages[(addr >> PAGE_SHIFT) + 1].addr;
+		u64 page_start = addr & (PAGE_SIZE - 1);
+		u64 first_len = PAGE_SIZE - (addr - page_start);
+
+		memcpy(to_buf, from_buf, first_len + metalen);
+		memcpy(next_pg_addr, from_buf + first_len, len - first_len);
+
+		return;
+	}
+
+	memcpy(to_buf, from_buf, len + metalen);
+}
+
 static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 {
-	void *to_buf, *from_buf;
+	u64 offset = xs->umem->headroom;
+	void *from_buf;
 	u32 metalen;
 	u64 addr;
 	int err;
 
-	if (!xskq_peek_addr(xs->umem->fq, &addr) ||
+	if (!xskq_peek_addr(xs->umem->fq, &addr, xs->umem) ||
 	    len > xs->umem->chunk_size_nohr - XDP_PACKET_HEADROOM) {
 		xs->rx_dropped++;
 		return -ENOSPC;
 	}
 
-	addr += xs->umem->headroom;
-
 	if (unlikely(xdp_data_meta_unsupported(xdp))) {
 		from_buf = xdp->data;
 		metalen = 0;
@@ -78,9 +99,13 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 		metalen = xdp->data - xdp->data_meta;
 	}
 
-	to_buf = xdp_umem_get_data(xs->umem, addr);
-	memcpy(to_buf, from_buf, len + metalen);
-	addr += metalen;
+	__xsk_rcv_memcpy(xs->umem, addr + offset, from_buf, len, metalen);
+
+	offset += metalen;
+	if (xs->umem->flags & XDP_UMEM_UNALIGNED_CHUNKS)
+		addr |= offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
+	else
+		addr += offset;
 	err = xskq_produce_batch_desc(xs->rx, addr, len);
 	if (!err) {
 		xskq_discard_addr(xs->umem->fq);
@@ -127,6 +152,7 @@ int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
 	u32 len = xdp->data_end - xdp->data;
 	void *buffer;
 	u64 addr;
+	u64 offset = xs->umem->headroom;
 	int err;
 
 	spin_lock_bh(&xs->rx_lock);
@@ -136,17 +162,20 @@ int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
 		goto out_unlock;
 	}
 
-	if (!xskq_peek_addr(xs->umem->fq, &addr) ||
+	if (!xskq_peek_addr(xs->umem->fq, &addr, xs->umem) ||
 	    len > xs->umem->chunk_size_nohr - XDP_PACKET_HEADROOM) {
 		err = -ENOSPC;
 		goto out_drop;
 	}
 
-	addr += xs->umem->headroom;
-
-	buffer = xdp_umem_get_data(xs->umem, addr);
+	buffer = xdp_umem_get_data(xs->umem, addr + offset);
 	memcpy(buffer, xdp->data_meta, len + metalen);
-	addr += metalen;
+	offset += metalen;
+
+	if (xs->umem->flags & XDP_UMEM_UNALIGNED_CHUNKS)
+		addr |= offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
+	else
+		addr += offset;
 	err = xskq_produce_batch_desc(xs->rx, addr, len);
 	if (err)
 		goto out_drop;
@@ -190,7 +219,7 @@ bool xsk_umem_consume_tx(struct xdp_umem *umem, struct xdp_desc *desc)
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(xs, &umem->xsk_list, list) {
-		if (!xskq_peek_desc(xs->tx, desc))
+		if (!xskq_peek_desc(xs->tx, desc, umem))
 			continue;
 
 		if (xskq_produce_addr_lazy(umem->cq, desc->addr))
@@ -240,7 +269,7 @@ static int xsk_generic_xmit(struct sock *sk, struct msghdr *m,
 
 	mutex_lock(&xs->mutex);
 
-	while (xskq_peek_desc(xs->tx, &desc)) {
+	while (xskq_peek_desc(xs->tx, &desc, xs->umem)) {
 		char *buffer;
 		u64 addr;
 		u32 len;
@@ -265,6 +294,10 @@ static int xsk_generic_xmit(struct sock *sk, struct msghdr *m,
 
 		skb_put(skb, len);
 		addr = desc.addr;
+		if (xs->umem->flags & XDP_UMEM_UNALIGNED_CHUNKS)
+			addr = (addr & XSK_UNALIGNED_BUF_ADDR_MASK) |
+				(addr >> XSK_UNALIGNED_BUF_OFFSET_SHIFT);
+
 		buffer = xdp_umem_get_data(xs->umem, addr);
 		err = skb_store_bits(skb, 0, buffer, len);
 		if (unlikely(err)) {
@@ -275,7 +308,7 @@ static int xsk_generic_xmit(struct sock *sk, struct msghdr *m,
 		skb->dev = xs->dev;
 		skb->priority = sk->sk_priority;
 		skb->mark = sk->sk_mark;
-		skb_shinfo(skb)->destructor_arg = (void *)(long)addr;
+		skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
 		skb->destructor = xsk_destruct_skb;
 
 		err = dev_direct_xmit(skb, xs->queue_id);
@@ -415,6 +448,28 @@ static struct socket *xsk_lookup_xsk_from_fd(int fd)
 	return sock;
 }
 
+/* Check if umem pages are contiguous.
+ * If zero-copy mode, use the DMA address to do the page contiguity check
+ * For all other modes we use addr (kernel virtual address)
+ */
+static void xsk_check_page_contiguity(struct xdp_umem *umem, u32 flags)
+{
+	int i;
+
+	if (flags & XDP_ZEROCOPY) {
+		for (i = 0; i < umem->npgs - 1; i++)
+			umem->pages[i].next_pg_contig =
+					(umem->pages[i].dma + PAGE_SIZE ==
+						umem->pages[i + 1].dma);
+		return;
+	}
+
+	for (i = 0; i < umem->npgs - 1; i++)
+		umem->pages[i].next_pg_contig =
+				(umem->pages[i].addr + PAGE_SIZE ==
+					umem->pages[i + 1].addr);
+}
+
 static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 {
 	struct sockaddr_xdp *sxdp = (struct sockaddr_xdp *)addr;
@@ -502,6 +557,8 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 		err = xdp_umem_assign_dev(xs->umem, dev, qid, flags);
 		if (err)
 			goto out_unlock;
+
+		xsk_check_page_contiguity(xs->umem, flags);
 	}
 
 	xs->dev = dev;
diff --git a/net/xdp/xsk_diag.c b/net/xdp/xsk_diag.c
index d5e06c8e0cbf..9986a759fe06 100644
--- a/net/xdp/xsk_diag.c
+++ b/net/xdp/xsk_diag.c
@@ -56,7 +56,7 @@ static int xsk_diag_put_umem(const struct xdp_sock *xs, struct sk_buff *nlskb)
 	du.id = umem->id;
 	du.size = umem->size;
 	du.num_pages = umem->npgs;
-	du.chunk_size = (__u32)(~umem->chunk_mask + 1);
+	du.chunk_size = umem->chunk_size_nohr + umem->headroom;
 	du.headroom = umem->headroom;
 	du.ifindex = umem->dev ? umem->dev->ifindex : 0;
 	du.queue_id = umem->queue_id;
diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index 909c5168ed0f..04afc9de86d9 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -133,6 +133,16 @@ static inline bool xskq_has_addrs(struct xsk_queue *q, u32 cnt)
 
 /* UMEM queue */
 
+static inline bool xskq_crosses_non_contig_pg(struct xdp_umem *umem, u64 addr,
+					      u64 length)
+{
+	bool cross_pg = (addr & (PAGE_SIZE - 1)) + length > PAGE_SIZE;
+	bool next_pg_contig =
+		umem->pages[(addr >> PAGE_SHIFT) + 1].next_pg_contig;
+
+	return cross_pg && !next_pg_contig;
+}
+
 static inline bool xskq_is_valid_addr(struct xsk_queue *q, u64 addr)
 {
 	if (addr >= q->size) {
@@ -143,23 +153,52 @@ static inline bool xskq_is_valid_addr(struct xsk_queue *q, u64 addr)
 	return true;
 }
 
-static inline u64 *xskq_validate_addr(struct xsk_queue *q, u64 *addr)
+static inline bool xskq_is_valid_addr_unaligned(struct xsk_queue *q, u64 addr,
+						u64 length,
+						struct xdp_umem *umem)
+{
+	addr += addr >> XSK_UNALIGNED_BUF_OFFSET_SHIFT;
+	addr &= XSK_UNALIGNED_BUF_ADDR_MASK;
+	if (addr >= q->size ||
+	    xskq_crosses_non_contig_pg(umem, addr, length)) {
+		q->invalid_descs++;
+		return false;
+	}
+
+	return true;
+}
+
+static inline u64 *xskq_validate_addr(struct xsk_queue *q, u64 *addr,
+				      struct xdp_umem *umem)
 {
 	while (q->cons_tail != q->cons_head) {
 		struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
 		unsigned int idx = q->cons_tail & q->ring_mask;
 
 		*addr = READ_ONCE(ring->desc[idx]) & q->chunk_mask;
+		if (*addr & (~XSK_UNALIGNED_BUF_ADDR_MASK))
+			goto out;
+
+		if (umem->flags & XDP_UMEM_UNALIGNED_CHUNKS) {
+			if (xskq_is_valid_addr_unaligned(q, *addr,
+							 umem->chunk_size_nohr,
+							 umem))
+				return addr;
+			goto out;
+		}
+
 		if (xskq_is_valid_addr(q, *addr))
 			return addr;
 
+out:
 		q->cons_tail++;
 	}
 
 	return NULL;
 }
 
-static inline u64 *xskq_peek_addr(struct xsk_queue *q, u64 *addr)
+static inline u64 *xskq_peek_addr(struct xsk_queue *q, u64 *addr,
+				  struct xdp_umem *umem)
 {
 	if (q->cons_tail == q->cons_head) {
 		smp_mb(); /* D, matches A */
@@ -170,7 +209,7 @@ static inline u64 *xskq_peek_addr(struct xsk_queue *q, u64 *addr)
 		smp_rmb();
 	}
 
-	return xskq_validate_addr(q, addr);
+	return xskq_validate_addr(q, addr, umem);
 }
 
 static inline void xskq_discard_addr(struct xsk_queue *q)
@@ -229,8 +268,21 @@ static inline int xskq_reserve_addr(struct xsk_queue *q)
 
 /* Rx/Tx queue */
 
-static inline bool xskq_is_valid_desc(struct xsk_queue *q, struct xdp_desc *d)
+static inline bool xskq_is_valid_desc(struct xsk_queue *q, struct xdp_desc *d,
+				      struct xdp_umem *umem)
 {
+	if (umem->flags & XDP_UMEM_UNALIGNED_CHUNKS) {
+		if (!xskq_is_valid_addr_unaligned(q, d->addr, d->len, umem))
+			return false;
+
+		if (d->len > umem->chunk_size_nohr || d->options) {
+			q->invalid_descs++;
+			return false;
+		}
+
+		return true;
+	}
+
 	if (!xskq_is_valid_addr(q, d->addr))
 		return false;
 
@@ -244,14 +296,15 @@ static inline bool xskq_is_valid_desc(struct xsk_queue *q, struct xdp_desc *d)
 }
 
 static inline struct xdp_desc *xskq_validate_desc(struct xsk_queue *q,
-						  struct xdp_desc *desc)
+						  struct xdp_desc *desc,
+						  struct xdp_umem *umem)
 {
 	while (q->cons_tail != q->cons_head) {
 		struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
 		unsigned int idx = q->cons_tail & q->ring_mask;
 
 		*desc = READ_ONCE(ring->desc[idx]);
-		if (xskq_is_valid_desc(q, desc))
+		if (xskq_is_valid_desc(q, desc, umem))
 			return desc;
 
 		q->cons_tail++;
@@ -261,7 +314,8 @@ static inline struct xdp_desc *xskq_validate_desc(struct xsk_queue *q,
 }
 
 static inline struct xdp_desc *xskq_peek_desc(struct xsk_queue *q,
-					      struct xdp_desc *desc)
+					      struct xdp_desc *desc,
+					      struct xdp_umem *umem)
 {
 	if (q->cons_tail == q->cons_head) {
 		smp_mb(); /* D, matches A */
@@ -272,7 +326,7 @@ static inline struct xdp_desc *xskq_peek_desc(struct xsk_queue *q,
 		smp_rmb(); /* C, matches B */
 	}
 
-	return xskq_validate_desc(q, desc);
+	return xskq_validate_desc(q, desc, umem);
 }
 
 static inline void xskq_discard_desc(struct xsk_queue *q)
-- 
2.17.1