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Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * AES optimized using the CP Assist for Cryptographic Functions (CPACF)
4 *
5 * Copyright 2026 Google LLC
6 */
7#include <asm/cpacf.h>
8#include <linux/cpufeature.h>
9
10static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_cpacf_aes128);
11static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_cpacf_aes192);
12static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_cpacf_aes256);
13
14/*
15 * When the CPU supports CPACF AES for the requested key length, we need only
16 * save a copy of the raw AES key, as that's what the CPACF instructions need.
17 *
18 * When unsupported, fall back to the generic key expansion and en/decryption.
19 */
20static void aes_preparekey_arch(union aes_enckey_arch *k,
21 union aes_invkey_arch *inv_k,
22 const u8 *in_key, int key_len, int nrounds)
23{
24 if (key_len == AES_KEYSIZE_128) {
25 if (static_branch_likely(&have_cpacf_aes128)) {
26 memcpy(k->raw_key, in_key, AES_KEYSIZE_128);
27 return;
28 }
29 } else if (key_len == AES_KEYSIZE_192) {
30 if (static_branch_likely(&have_cpacf_aes192)) {
31 memcpy(k->raw_key, in_key, AES_KEYSIZE_192);
32 return;
33 }
34 } else {
35 if (static_branch_likely(&have_cpacf_aes256)) {
36 memcpy(k->raw_key, in_key, AES_KEYSIZE_256);
37 return;
38 }
39 }
40 aes_expandkey_generic(k->rndkeys, inv_k ? inv_k->inv_rndkeys : NULL,
41 in_key, key_len);
42}
43
44static inline bool aes_crypt_s390(const struct aes_enckey *key,
45 u8 out[AES_BLOCK_SIZE],
46 const u8 in[AES_BLOCK_SIZE], int decrypt)
47{
48 if (key->len == AES_KEYSIZE_128) {
49 if (static_branch_likely(&have_cpacf_aes128)) {
50 cpacf_km(CPACF_KM_AES_128 | decrypt,
51 (void *)key->k.raw_key, out, in,
52 AES_BLOCK_SIZE);
53 return true;
54 }
55 } else if (key->len == AES_KEYSIZE_192) {
56 if (static_branch_likely(&have_cpacf_aes192)) {
57 cpacf_km(CPACF_KM_AES_192 | decrypt,
58 (void *)key->k.raw_key, out, in,
59 AES_BLOCK_SIZE);
60 return true;
61 }
62 } else {
63 if (static_branch_likely(&have_cpacf_aes256)) {
64 cpacf_km(CPACF_KM_AES_256 | decrypt,
65 (void *)key->k.raw_key, out, in,
66 AES_BLOCK_SIZE);
67 return true;
68 }
69 }
70 return false;
71}
72
73static void aes_encrypt_arch(const struct aes_enckey *key,
74 u8 out[AES_BLOCK_SIZE],
75 const u8 in[AES_BLOCK_SIZE])
76{
77 if (likely(aes_crypt_s390(key, out, in, 0)))
78 return;
79 aes_encrypt_generic(key->k.rndkeys, key->nrounds, out, in);
80}
81
82static void aes_decrypt_arch(const struct aes_key *key,
83 u8 out[AES_BLOCK_SIZE],
84 const u8 in[AES_BLOCK_SIZE])
85{
86 if (likely(aes_crypt_s390((const struct aes_enckey *)key, out, in,
87 CPACF_DECRYPT)))
88 return;
89 aes_decrypt_generic(key->inv_k.inv_rndkeys, key->nrounds, out, in);
90}
91
92#define aes_mod_init_arch aes_mod_init_arch
93static void aes_mod_init_arch(void)
94{
95 if (cpu_have_feature(S390_CPU_FEATURE_MSA)) {
96 cpacf_mask_t km_functions;
97
98 cpacf_query(CPACF_KM, &km_functions);
99 if (cpacf_test_func(&km_functions, CPACF_KM_AES_128))
100 static_branch_enable(&have_cpacf_aes128);
101 if (cpacf_test_func(&km_functions, CPACF_KM_AES_192))
102 static_branch_enable(&have_cpacf_aes192);
103 if (cpacf_test_func(&km_functions, CPACF_KM_AES_256))
104 static_branch_enable(&have_cpacf_aes256);
105 }
106}