Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next

Pull networking updates from David Miller:
 "Highlights:

   1) Support AES128-CCM ciphers in kTLS, from Vakul Garg.

   2) Add fib_sync_mem to control the amount of dirty memory we allow to
      queue up between synchronize RCU calls, from David Ahern.

   3) Make flow classifier more lockless, from Vlad Buslov.

   4) Add PHY downshift support to aquantia driver, from Heiner
      Kallweit.

   5) Add SKB cache for TCP rx and tx, from Eric Dumazet. This reduces
      contention on SLAB spinlocks in heavy RPC workloads.

   6) Partial GSO offload support in XFRM, from Boris Pismenny.

   7) Add fast link down support to ethtool, from Heiner Kallweit.

   8) Use siphash for IP ID generator, from Eric Dumazet.

   9) Pull nexthops even further out from ipv4/ipv6 routes and FIB
      entries, from David Ahern.

  10) Move skb->xmit_more into a per-cpu variable, from Florian
      Westphal.

  11) Improve eBPF verifier speed and increase maximum program size,
      from Alexei Starovoitov.

  12) Eliminate per-bucket spinlocks in rhashtable, and instead use bit
      spinlocks. From Neil Brown.

  13) Allow tunneling with GUE encap in ipvs, from Jacky Hu.

  14) Improve link partner cap detection in generic PHY code, from
      Heiner Kallweit.

  15) Add layer 2 encap support to bpf_skb_adjust_room(), from Alan
      Maguire.

  16) Remove SKB list implementation assumptions in SCTP, your's truly.

  17) Various cleanups, optimizations, and simplifications in r8169
      driver. From Heiner Kallweit.

  18) Add memory accounting on TX and RX path of SCTP, from Xin Long.

  19) Switch PHY drivers over to use dynamic featue detection, from
      Heiner Kallweit.

  20) Support flow steering without masking in dpaa2-eth, from Ioana
      Ciocoi.

  21) Implement ndo_get_devlink_port in netdevsim driver, from Jiri
      Pirko.

  22) Increase the strict parsing of current and future netlink
      attributes, also export such policies to userspace. From Johannes
      Berg.

  23) Allow DSA tag drivers to be modular, from Andrew Lunn.

  24) Remove legacy DSA probing support, also from Andrew Lunn.

  25) Allow ll_temac driver to be used on non-x86 platforms, from Esben
      Haabendal.

  26) Add a generic tracepoint for TX queue timeouts to ease debugging,
      from Cong Wang.

  27) More indirect call optimizations, from Paolo Abeni"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1763 commits)
  cxgb4: Fix error path in cxgb4_init_module
  net: phy: improve pause mode reporting in phy_print_status
  dt-bindings: net: Fix a typo in the phy-mode list for ethernet bindings
  net: macb: Change interrupt and napi enable order in open
  net: ll_temac: Improve error message on error IRQ
  net/sched: remove block pointer from common offload structure
  net: ethernet: support of_get_mac_address new ERR_PTR error
  net: usb: smsc: fix warning reported by kbuild test robot
  staging: octeon-ethernet: Fix of_get_mac_address ERR_PTR check
  net: dsa: support of_get_mac_address new ERR_PTR error
  net: dsa: sja1105: Fix status initialization in sja1105_get_ethtool_stats
  vrf: sit mtu should not be updated when vrf netdev is the link
  net: dsa: Fix error cleanup path in dsa_init_module
  l2tp: Fix possible NULL pointer dereference
  taprio: add null check on sched_nest to avoid potential null pointer dereference
  net: mvpp2: cls: fix less than zero check on a u32 variable
  net_sched: sch_fq: handle non connected flows
  net_sched: sch_fq: do not assume EDT packets are ordered
  net: hns3: use devm_kcalloc when allocating desc_cb
  net: hns3: some cleanup for struct hns3_enet_ring
  ...

1 files changed, 52 insertions, 4 deletions

diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index 610c0bdc0c2b..88b9ae24658d 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -43,6 +43,48 @@ struct xsk_queue {
 	u64 invalid_descs;
 };
 
+/* The structure of the shared state of the rings are the same as the
+ * ring buffer in kernel/events/ring_buffer.c. 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) {           LOAD ->producer
+ *                    (A)           smp_rmb()       (C)
+ *    STORE $data                   LOAD $data
+ *    smp_wmb()       (B)           smp_mb()        (D)
+ *    STORE ->producer              STORE ->consumer
+ * }
+ *
+ * (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. 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.
+ */
+
 /* Common functions operating for both RXTX and umem queues */
 
 static inline u64 xskq_nb_invalid_descs(struct xsk_queue *q)
@@ -106,6 +148,7 @@ static inline u64 *xskq_validate_addr(struct xsk_queue *q, u64 *addr)
 static inline u64 *xskq_peek_addr(struct xsk_queue *q, u64 *addr)
 {
 	if (q->cons_tail == q->cons_head) {
+		smp_mb(); /* D, matches A */
 		WRITE_ONCE(q->ring->consumer, q->cons_tail);
 		q->cons_head = q->cons_tail + xskq_nb_avail(q, RX_BATCH_SIZE);
 
@@ -128,10 +171,11 @@ static inline int xskq_produce_addr(struct xsk_queue *q, u64 addr)
 	if (xskq_nb_free(q, q->prod_tail, 1) == 0)
 		return -ENOSPC;
 
+	/* A, matches D */
 	ring->desc[q->prod_tail++ & q->ring_mask] = addr;
 
 	/* Order producer and data */
-	smp_wmb();
+	smp_wmb(); /* B, matches C */
 
 	WRITE_ONCE(q->ring->producer, q->prod_tail);
 	return 0;
@@ -144,6 +188,7 @@ static inline int xskq_produce_addr_lazy(struct xsk_queue *q, u64 addr)
 	if (xskq_nb_free(q, q->prod_head, LAZY_UPDATE_THRESHOLD) == 0)
 		return -ENOSPC;
 
+	/* A, matches D */
 	ring->desc[q->prod_head++ & q->ring_mask] = addr;
 	return 0;
 }
@@ -152,7 +197,7 @@ static inline void xskq_produce_flush_addr_n(struct xsk_queue *q,
 					     u32 nb_entries)
 {
 	/* Order producer and data */
-	smp_wmb();
+	smp_wmb(); /* B, matches C */
 
 	q->prod_tail += nb_entries;
 	WRITE_ONCE(q->ring->producer, q->prod_tail);
@@ -163,6 +208,7 @@ static inline int xskq_reserve_addr(struct xsk_queue *q)
 	if (xskq_nb_free(q, q->prod_head, 1) == 0)
 		return -ENOSPC;
 
+	/* A, matches D */
 	q->prod_head++;
 	return 0;
 }
@@ -204,11 +250,12 @@ static inline struct xdp_desc *xskq_peek_desc(struct xsk_queue *q,
 					      struct xdp_desc *desc)
 {
 	if (q->cons_tail == q->cons_head) {
+		smp_mb(); /* D, matches A */
 		WRITE_ONCE(q->ring->consumer, q->cons_tail);
 		q->cons_head = q->cons_tail + xskq_nb_avail(q, RX_BATCH_SIZE);
 
 		/* Order consumer and data */
-		smp_rmb();
+		smp_rmb(); /* C, matches B */
 	}
 
 	return xskq_validate_desc(q, desc);
@@ -228,6 +275,7 @@ static inline int xskq_produce_batch_desc(struct xsk_queue *q,
 	if (xskq_nb_free(q, q->prod_head, 1) == 0)
 		return -ENOSPC;
 
+	/* A, matches D */
 	idx = (q->prod_head++) & q->ring_mask;
 	ring->desc[idx].addr = addr;
 	ring->desc[idx].len = len;
@@ -238,7 +286,7 @@ static inline int xskq_produce_batch_desc(struct xsk_queue *q,
 static inline void xskq_produce_flush_desc(struct xsk_queue *q)
 {
 	/* Order producer and data */
-	smp_wmb();
+	smp_wmb(); /* B, matches C */
 
 	q->prod_tail = q->prod_head,
 	WRITE_ONCE(q->ring->producer, q->prod_tail);