nfp: bpf: add simple map op cache

Each get_next and lookup call requires a round trip to the device.
However, the device is capable of giving us a few entries back,
instead of just one.

In this patch we ask for a small yet reasonable number of entries
(4) on every get_next call, and on subsequent get_next/lookup calls
check this little cache for a hit. The cache is only kept for 250us,
and is invalidated on every operation which may modify the map
(e.g. delete or update call). Note that operations may be performed
simultaneously, so we have to keep track of operations in flight.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 170 insertions, 9 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c b/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c
index fcf880c82f3f..0e2db6ea79e9 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c
@@ -6,6 +6,7 @@
 #include <linux/bug.h>
 #include <linux/jiffies.h>
 #include <linux/skbuff.h>
+#include <linux/timekeeping.h>
 
 #include "../ccm.h"
 #include "../nfp_app.h"
@@ -175,29 +176,151 @@ nfp_bpf_ctrl_reply_val(struct nfp_app_bpf *bpf, struct cmsg_reply_map_op *reply,
 	return &reply->data[bpf->cmsg_key_sz * (n + 1) + bpf->cmsg_val_sz * n];
 }
 
+static bool nfp_bpf_ctrl_op_cache_invalidate(enum nfp_ccm_type op)
+{
+	return op == NFP_CCM_TYPE_BPF_MAP_UPDATE ||
+	       op == NFP_CCM_TYPE_BPF_MAP_DELETE;
+}
+
+static bool nfp_bpf_ctrl_op_cache_capable(enum nfp_ccm_type op)
+{
+	return op == NFP_CCM_TYPE_BPF_MAP_LOOKUP ||
+	       op == NFP_CCM_TYPE_BPF_MAP_GETNEXT;
+}
+
+static bool nfp_bpf_ctrl_op_cache_fill(enum nfp_ccm_type op)
+{
+	return op == NFP_CCM_TYPE_BPF_MAP_GETFIRST ||
+	       op == NFP_CCM_TYPE_BPF_MAP_GETNEXT;
+}
+
+static unsigned int
+nfp_bpf_ctrl_op_cache_get(struct nfp_bpf_map *nfp_map, enum nfp_ccm_type op,
+			  const u8 *key, u8 *out_key, u8 *out_value,
+			  u32 *cache_gen)
+{
+	struct bpf_map *map = &nfp_map->offmap->map;
+	struct nfp_app_bpf *bpf = nfp_map->bpf;
+	unsigned int i, count, n_entries;
+	struct cmsg_reply_map_op *reply;
+
+	n_entries = nfp_bpf_ctrl_op_cache_fill(op) ? bpf->cmsg_cache_cnt : 1;
+
+	spin_lock(&nfp_map->cache_lock);
+	*cache_gen = nfp_map->cache_gen;
+	if (nfp_map->cache_blockers)
+		n_entries = 1;
+
+	if (nfp_bpf_ctrl_op_cache_invalidate(op))
+		goto exit_block;
+	if (!nfp_bpf_ctrl_op_cache_capable(op))
+		goto exit_unlock;
+
+	if (!nfp_map->cache)
+		goto exit_unlock;
+	if (nfp_map->cache_to < ktime_get_ns())
+		goto exit_invalidate;
+
+	reply = (void *)nfp_map->cache->data;
+	count = be32_to_cpu(reply->count);
+
+	for (i = 0; i < count; i++) {
+		void *cached_key;
+
+		cached_key = nfp_bpf_ctrl_reply_key(bpf, reply, i);
+		if (memcmp(cached_key, key, map->key_size))
+			continue;
+
+		if (op == NFP_CCM_TYPE_BPF_MAP_LOOKUP)
+			memcpy(out_value, nfp_bpf_ctrl_reply_val(bpf, reply, i),
+			       map->value_size);
+		if (op == NFP_CCM_TYPE_BPF_MAP_GETNEXT) {
+			if (i + 1 == count)
+				break;
+
+			memcpy(out_key,
+			       nfp_bpf_ctrl_reply_key(bpf, reply, i + 1),
+			       map->key_size);
+		}
+
+		n_entries = 0;
+		goto exit_unlock;
+	}
+	goto exit_unlock;
+
+exit_block:
+	nfp_map->cache_blockers++;
+exit_invalidate:
+	dev_consume_skb_any(nfp_map->cache);
+	nfp_map->cache = NULL;
+exit_unlock:
+	spin_unlock(&nfp_map->cache_lock);
+	return n_entries;
+}
+
+static void
+nfp_bpf_ctrl_op_cache_put(struct nfp_bpf_map *nfp_map, enum nfp_ccm_type op,
+			  struct sk_buff *skb, u32 cache_gen)
+{
+	bool blocker, filler;
+
+	blocker = nfp_bpf_ctrl_op_cache_invalidate(op);
+	filler = nfp_bpf_ctrl_op_cache_fill(op);
+	if (blocker || filler) {
+		u64 to = 0;
+
+		if (filler)
+			to = ktime_get_ns() + NFP_BPF_MAP_CACHE_TIME_NS;
+
+		spin_lock(&nfp_map->cache_lock);
+		if (blocker) {
+			nfp_map->cache_blockers--;
+			nfp_map->cache_gen++;
+		}
+		if (filler && !nfp_map->cache_blockers &&
+		    nfp_map->cache_gen == cache_gen) {
+			nfp_map->cache_to = to;
+			swap(nfp_map->cache, skb);
+		}
+		spin_unlock(&nfp_map->cache_lock);
+	}
+
+	dev_consume_skb_any(skb);
+}
+
 static int
 nfp_bpf_ctrl_entry_op(struct bpf_offloaded_map *offmap, enum nfp_ccm_type op,
 		      u8 *key, u8 *value, u64 flags, u8 *out_key, u8 *out_value)
 {
 	struct nfp_bpf_map *nfp_map = offmap->dev_priv;
+	unsigned int n_entries, reply_entries, count;
 	struct nfp_app_bpf *bpf = nfp_map->bpf;
 	struct bpf_map *map = &offmap->map;
 	struct cmsg_reply_map_op *reply;
 	struct cmsg_req_map_op *req;
 	struct sk_buff *skb;
+	u32 cache_gen;
 	int err;
 
 	/* FW messages have no space for more than 32 bits of flags */
 	if (flags >> 32)
 		return -EOPNOTSUPP;
 
+	/* Handle op cache */
+	n_entries = nfp_bpf_ctrl_op_cache_get(nfp_map, op, key, out_key,
+					      out_value, &cache_gen);
+	if (!n_entries)
+		return 0;
+
 	skb = nfp_bpf_cmsg_map_req_alloc(bpf, 1);
-	if (!skb)
-		return -ENOMEM;
+	if (!skb) {
+		err = -ENOMEM;
+		goto err_cache_put;
+	}
 
 	req = (void *)skb->data;
 	req->tid = cpu_to_be32(nfp_map->tid);
-	req->count = cpu_to_be32(1);
+	req->count = cpu_to_be32(n_entries);
 	req->flags = cpu_to_be32(flags);
 
 	/* Copy inputs */
@@ -207,16 +330,38 @@ nfp_bpf_ctrl_entry_op(struct bpf_offloaded_map *offmap, enum nfp_ccm_type op,
 		memcpy(nfp_bpf_ctrl_req_val(bpf, req, 0), value,
 		       map->value_size);
 
-	skb = nfp_ccm_communicate(&bpf->ccm, skb, op,
-				  nfp_bpf_cmsg_map_reply_size(bpf, 1));
-	if (IS_ERR(skb))
-		return PTR_ERR(skb);
+	skb = nfp_ccm_communicate(&bpf->ccm, skb, op, 0);
+	if (IS_ERR(skb)) {
+		err = PTR_ERR(skb);
+		goto err_cache_put;
+	}
+
+	if (skb->len < sizeof(*reply)) {
+		cmsg_warn(bpf, "cmsg drop - type 0x%02x too short %d!\n",
+			  op, skb->len);
+		err = -EIO;
+		goto err_free;
+	}
 
 	reply = (void *)skb->data;
+	count = be32_to_cpu(reply->count);
 	err = nfp_bpf_ctrl_rc_to_errno(bpf, &reply->reply_hdr);
+	/* FW responds with message sized to hold the good entries,
+	 * plus one extra entry if there was an error.
+	 */
+	reply_entries = count + !!err;
+	if (n_entries > 1 && count)
+		err = 0;
 	if (err)
 		goto err_free;
 
+	if (skb->len != nfp_bpf_cmsg_map_reply_size(bpf, reply_entries)) {
+		cmsg_warn(bpf, "cmsg drop - type 0x%02x too short %d for %d entries!\n",
+			  op, skb->len, reply_entries);
+		err = -EIO;
+		goto err_free;
+	}
+
 	/* Copy outputs */
 	if (out_key)
 		memcpy(out_key, nfp_bpf_ctrl_reply_key(bpf, reply, 0),
@@ -225,11 +370,13 @@ nfp_bpf_ctrl_entry_op(struct bpf_offloaded_map *offmap, enum nfp_ccm_type op,
 		memcpy(out_value, nfp_bpf_ctrl_reply_val(bpf, reply, 0),
 		       map->value_size);
 
-	dev_consume_skb_any(skb);
+	nfp_bpf_ctrl_op_cache_put(nfp_map, op, skb, cache_gen);
 
 	return 0;
 err_free:
 	dev_kfree_skb_any(skb);
+err_cache_put:
+	nfp_bpf_ctrl_op_cache_put(nfp_map, op, NULL, cache_gen);
 	return err;
 }
 
@@ -275,7 +422,21 @@ unsigned int nfp_bpf_ctrl_cmsg_min_mtu(struct nfp_app_bpf *bpf)
 
 unsigned int nfp_bpf_ctrl_cmsg_mtu(struct nfp_app_bpf *bpf)
 {
-	return max(NFP_NET_DEFAULT_MTU, nfp_bpf_ctrl_cmsg_min_mtu(bpf));
+	return max3(NFP_NET_DEFAULT_MTU,
+		    nfp_bpf_cmsg_map_req_size(bpf, NFP_BPF_MAP_CACHE_CNT),
+		    nfp_bpf_cmsg_map_reply_size(bpf, NFP_BPF_MAP_CACHE_CNT));
+}
+
+unsigned int nfp_bpf_ctrl_cmsg_cache_cnt(struct nfp_app_bpf *bpf)
+{
+	unsigned int mtu, req_max, reply_max, entry_sz;
+
+	mtu = bpf->app->ctrl->dp.mtu;
+	entry_sz = bpf->cmsg_key_sz + bpf->cmsg_val_sz;
+	req_max = (mtu - sizeof(struct cmsg_req_map_op)) / entry_sz;
+	reply_max = (mtu - sizeof(struct cmsg_reply_map_op)) / entry_sz;
+
+	return min3(req_max, reply_max, NFP_BPF_MAP_CACHE_CNT);
 }
 
 void nfp_bpf_ctrl_msg_rx(struct nfp_app *app, struct sk_buff *skb)