nft_set_pipapo: Prepare for single ranged field usage

A few adjustments in nft_pipapo_init() are needed to allow usage of
this set back-end for a single, ranged field.

Provide a convenient NFT_PIPAPO_MIN_FIELDS definition that currently
makes sure that the rbtree back-end is selected instead, for sets
with a single field.

This finally allows a fair comparison with rbtree sets, by defining
NFT_PIPAPO_MIN_FIELDS as 0 and skipping rbtree back-end initialisation:

---------------.--------------------------.-------------------------.
AMD Epyc 7402 | baselines, Mpps | Mpps, % over rbtree |
1 thread |__________________________|_________________________|
3.35GHz | | | | | |
768KiB L1D$ | netdev | hash | rbtree | | pipapo |
---------------| hook | no | single | pipapo |single field|
type entries | drop | ranges | field |single field| AVX2 |
---------------|--------|--------|--------|------------|------------|
net,port | | | | | |
1000 | 19.0 | 10.4 | 3.8 | 6.0 +58% | 9.6 +153% |
---------------|--------|--------|--------|------------|------------|
port,net | | | | | |
100 | 18.8 | 10.3 | 5.8 | 9.1 +57% |11.6 +100% |
---------------|--------|--------|--------|------------|------------|
net6,port | | | | | |
1000 | 16.4 | 7.6 | 1.8 | 2.8 +55% | 6.5 +261% |
---------------|--------|--------|--------|------------|------------|
port,proto | | | | [1] | [1] |
30000 | 19.6 | 11.6 | 3.9 | 0.9 -77% | 2.7 -31% |
---------------|--------|--------|--------|------------|------------|
port,proto | | | | | |
10000 | 19.6 | 11.6 | 4.4 | 2.1 -52% | 5.6 +27% |
---------------|--------|--------|--------|------------|------------|
port,proto | | | | | |
4 threads 10000| 77.9 | 45.1 | 17.4 | 8.3 -52% |22.4 +29% |
---------------|--------|--------|--------|------------|------------|
net6,port,mac | | | | | |
10 | 16.5 | 5.4 | 4.3 | 4.5 +5% | 8.2 +91% |
---------------|--------|--------|--------|------------|------------|
net6,port,mac, | | | | | |
proto 1000 | 16.5 | 5.7 | 1.9 | 2.8 +47% | 6.6 +247% |
---------------|--------|--------|--------|------------|------------|
net,mac | | | | | |
1000 | 19.0 | 8.4 | 3.9 | 6.0 +54% | 9.9 +154% |
---------------'--------'--------'--------'------------'------------'
[1] Causes switch of lookup table buckets for 'port' to 4-bit groups

Signed-off-by: Stefano Brivio <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/netfilter/nft_set_pipapo.c

···
 static bool nft_pipapo_estimate(const struct nft_set_desc *desc, u32 features,
 				struct nft_set_estimate *est)
 {
-	if (!(features & NFT_SET_INTERVAL) || desc->field_count <= 1)
+	if (!(features & NFT_SET_INTERVAL) ||
+	    desc->field_count < NFT_PIPAPO_MIN_FIELDS)
 		return false;
 
 	est->size = pipapo_estimate_size(desc);
···
 	struct nft_pipapo *priv = nft_set_priv(set);
 	struct nft_pipapo_match *m;
 	struct nft_pipapo_field *f;
-	int err, i;
+	int err, i, field_count;
 
-	if (desc->field_count > NFT_PIPAPO_MAX_FIELDS)
+	field_count = desc->field_count ? : 1;
+
+	if (field_count > NFT_PIPAPO_MAX_FIELDS)
 		return -EINVAL;
 
-	m = kmalloc(sizeof(*priv->match) + sizeof(*f) * desc->field_count,
+	m = kmalloc(sizeof(*priv->match) + sizeof(*f) * field_count,
 		    GFP_KERNEL);
 	if (!m)
 		return -ENOMEM;
 
-	m->field_count = desc->field_count;
+	m->field_count = field_count;
 	m->bsize_max = 0;
 
 	m->scratch = alloc_percpu(unsigned long *);
···
 	rcu_head_init(&m->rcu);
 
 	nft_pipapo_for_each_field(f, i, m) {
-		f->bb = NFT_PIPAPO_GROUP_BITS_INIT;
-		f->groups = desc->field_len[i] * NFT_PIPAPO_GROUPS_PER_BYTE(f);
+		int len = desc->field_len[i] ? : set->klen;
 
-		priv->width += round_up(desc->field_len[i], sizeof(u32));
+		f->bb = NFT_PIPAPO_GROUP_BITS_INIT;
+		f->groups = len * NFT_PIPAPO_GROUPS_PER_BYTE(f);
+
+		priv->width += round_up(len, sizeof(u32));
 
 		f->bsize = 0;
 		f->rules = 0;

net/netfilter/nft_set_pipapo.h

···
 /* Count of concatenated fields depends on count of 32-bit nftables registers */
 #define NFT_PIPAPO_MAX_FIELDS		NFT_REG32_COUNT
 
+/* Restrict usage to multiple fields, make sure rbtree is used otherwise */
+#define NFT_PIPAPO_MIN_FIELDS		2
+
 /* Largest supported field size */
 #define NFT_PIPAPO_MAX_BYTES		(sizeof(struct in6_addr))
 #define NFT_PIPAPO_MAX_BITS		(NFT_PIPAPO_MAX_BYTES * BITS_PER_BYTE)

net/netfilter/nft_set_pipapo_avx2.c

···
 bool nft_pipapo_avx2_estimate(const struct nft_set_desc *desc, u32 features,
 			      struct nft_set_estimate *est)
 {
-	if (!(features & NFT_SET_INTERVAL) || desc->field_count <= 1)
+	if (!(features & NFT_SET_INTERVAL) ||
+	    desc->field_count < NFT_PIPAPO_MIN_FIELDS)
 		return false;
 
 	if (!boot_cpu_has(X86_FEATURE_AVX2) || !boot_cpu_has(X86_FEATURE_AVX))