selftests: bpf: crypto: adjust bench to use nullable IV

The bench shows some improvements, around 4% faster on decrypt.

Before:

Benchmark 'crypto-decrypt' started.
Iter 0 (325.719us): hits 5.105M/s ( 5.105M/prod), drops 0.000M/s, total operations 5.105M/s
Iter 1 (-17.295us): hits 5.224M/s ( 5.224M/prod), drops 0.000M/s, total operations 5.224M/s
Iter 2 ( 5.504us): hits 4.630M/s ( 4.630M/prod), drops 0.000M/s, total operations 4.630M/s
Iter 3 ( 9.239us): hits 5.148M/s ( 5.148M/prod), drops 0.000M/s, total operations 5.148M/s
Iter 4 ( 37.885us): hits 5.198M/s ( 5.198M/prod), drops 0.000M/s, total operations 5.198M/s
Iter 5 (-53.282us): hits 5.167M/s ( 5.167M/prod), drops 0.000M/s, total operations 5.167M/s
Iter 6 (-17.809us): hits 5.186M/s ( 5.186M/prod), drops 0.000M/s, total operations 5.186M/s
Summary: hits 5.092 ± 0.228M/s ( 5.092M/prod), drops 0.000 ±0.000M/s, total operations 5.092 ± 0.228M/s

After:

Benchmark 'crypto-decrypt' started.
Iter 0 (268.912us): hits 5.312M/s ( 5.312M/prod), drops 0.000M/s, total operations 5.312M/s
Iter 1 (124.869us): hits 5.354M/s ( 5.354M/prod), drops 0.000M/s, total operations 5.354M/s
Iter 2 (-36.801us): hits 5.334M/s ( 5.334M/prod), drops 0.000M/s, total operations 5.334M/s
Iter 3 (254.628us): hits 5.334M/s ( 5.334M/prod), drops 0.000M/s, total operations 5.334M/s
Iter 4 (-77.691us): hits 5.275M/s ( 5.275M/prod), drops 0.000M/s, total operations 5.275M/s
Iter 5 (-164.510us): hits 5.313M/s ( 5.313M/prod), drops 0.000M/s, total operations 5.313M/s
Iter 6 (-81.376us): hits 5.346M/s ( 5.346M/prod), drops 0.000M/s, total operations 5.346M/s
Summary: hits 5.326 ± 0.029M/s ( 5.326M/prod), drops 0.000 ±0.000M/s, total operations 5.326 ± 0.029M/s

Reviewed-by: Eduard Zingerman <[e-mail]>
Signed-off-by: Vadim Fedorenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/progs/crypto_bench.c

···
 {
 	struct __crypto_ctx_value *v;
 	struct bpf_crypto_ctx *ctx;
-	struct bpf_dynptr psrc, pdst, iv;
+	struct bpf_dynptr psrc, pdst;
 
 	v = crypto_ctx_value_lookup();
 	if (!v) {
···
 
 	bpf_dynptr_from_skb(skb, 0, &psrc);
 	bpf_dynptr_from_mem(dst, len, 0, &pdst);
-	bpf_dynptr_from_mem(dst, 0, 0, &iv);
 
-	status = bpf_crypto_encrypt(ctx, &psrc, &pdst, &iv);
+	status = bpf_crypto_encrypt(ctx, &psrc, &pdst, NULL);
 	__sync_add_and_fetch(&hits, 1);
 
 	return 0;
···
 SEC("tc")
 int crypto_decrypt(struct __sk_buff *skb)
 {
-	struct bpf_dynptr psrc, pdst, iv;
+	struct bpf_dynptr psrc, pdst;
 	struct __crypto_ctx_value *v;
 	struct bpf_crypto_ctx *ctx;
 
···
 
 	bpf_dynptr_from_skb(skb, 0, &psrc);
 	bpf_dynptr_from_mem(dst, len, 0, &pdst);
-	bpf_dynptr_from_mem(dst, 0, 0, &iv);
 
-	status = bpf_crypto_decrypt(ctx, &psrc, &pdst, &iv);
+	status = bpf_crypto_decrypt(ctx, &psrc, &pdst, NULL);
 	__sync_add_and_fetch(&hits, 1);
 
 	return 0;