1 files changed, 106 insertions, 0 deletions
diff --git a/lib/crypto/s390/aes.h b/lib/crypto/s390/aes.h
new file mode 100644
index 000000000..5466f6ecb
--- /dev/null
+++ b/lib/crypto/s390/aes.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * AES optimized using the CP Assist for Cryptographic Functions (CPACF)
+ *
+ * Copyright 2026 Google LLC
+ */
+#include <asm/cpacf.h>
+#include <linux/cpufeature.h>
+
+static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_cpacf_aes128);
+static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_cpacf_aes192);
+static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_cpacf_aes256);
+
+/*
+ * When the CPU supports CPACF AES for the requested key length, we need only
+ * save a copy of the raw AES key, as that's what the CPACF instructions need.
+ *
+ * When unsupported, fall back to the generic key expansion and en/decryption.
+ */
+static void aes_preparekey_arch(union aes_enckey_arch *k,
+				union aes_invkey_arch *inv_k,
+				const u8 *in_key, int key_len, int nrounds)
+{
+	if (key_len == AES_KEYSIZE_128) {
+		if (static_branch_likely(&have_cpacf_aes128)) {
+			memcpy(k->raw_key, in_key, AES_KEYSIZE_128);
+			return;
+		}
+	} else if (key_len == AES_KEYSIZE_192) {
+		if (static_branch_likely(&have_cpacf_aes192)) {
+			memcpy(k->raw_key, in_key, AES_KEYSIZE_192);
+			return;
+		}
+	} else {
+		if (static_branch_likely(&have_cpacf_aes256)) {
+			memcpy(k->raw_key, in_key, AES_KEYSIZE_256);
+			return;
+		}
+	}
+	aes_expandkey_generic(k->rndkeys, inv_k ? inv_k->inv_rndkeys : NULL,
+			      in_key, key_len);
+}
+
+static inline bool aes_crypt_s390(const struct aes_enckey *key,
+				  u8 out[AES_BLOCK_SIZE],
+				  const u8 in[AES_BLOCK_SIZE], int decrypt)
+{
+	if (key->len == AES_KEYSIZE_128) {
+		if (static_branch_likely(&have_cpacf_aes128)) {
+			cpacf_km(CPACF_KM_AES_128 | decrypt,
+				 (void *)key->k.raw_key, out, in,
+				 AES_BLOCK_SIZE);
+			return true;
+		}
+	} else if (key->len == AES_KEYSIZE_192) {
+		if (static_branch_likely(&have_cpacf_aes192)) {
+			cpacf_km(CPACF_KM_AES_192 | decrypt,
+				 (void *)key->k.raw_key, out, in,
+				 AES_BLOCK_SIZE);
+			return true;
+		}
+	} else {
+		if (static_branch_likely(&have_cpacf_aes256)) {
+			cpacf_km(CPACF_KM_AES_256 | decrypt,
+				 (void *)key->k.raw_key, out, in,
+				 AES_BLOCK_SIZE);
+			return true;
+		}
+	}
+	return false;
+}
+
+static void aes_encrypt_arch(const struct aes_enckey *key,
+			     u8 out[AES_BLOCK_SIZE],
+			     const u8 in[AES_BLOCK_SIZE])
+{
+	if (likely(aes_crypt_s390(key, out, in, 0)))
+		return;
+	aes_encrypt_generic(key->k.rndkeys, key->nrounds, out, in);
+}
+
+static void aes_decrypt_arch(const struct aes_key *key,
+			     u8 out[AES_BLOCK_SIZE],
+			     const u8 in[AES_BLOCK_SIZE])
+{
+	if (likely(aes_crypt_s390((const struct aes_enckey *)key, out, in,
+				  CPACF_DECRYPT)))
+		return;
+	aes_decrypt_generic(key->inv_k.inv_rndkeys, key->nrounds, out, in);
+}
+
+#define aes_mod_init_arch aes_mod_init_arch
+static void aes_mod_init_arch(void)
+{
+	if (cpu_have_feature(S390_CPU_FEATURE_MSA)) {
+		cpacf_mask_t km_functions;
+
+		cpacf_query(CPACF_KM, &km_functions);
+		if (cpacf_test_func(&km_functions, CPACF_KM_AES_128))
+			static_branch_enable(&have_cpacf_aes128);
+		if (cpacf_test_func(&km_functions, CPACF_KM_AES_192))
+			static_branch_enable(&have_cpacf_aes192);
+		if (cpacf_test_func(&km_functions, CPACF_KM_AES_256))
+			static_branch_enable(&have_cpacf_aes256);
+	}
+}