[PATCH 3/8] Revert "crypto: x86/sha256 - Add simd block function"

[Eric Biggers <ebiggers@kernel.org>]

From: Eric Biggers <ebiggers@google.com>

This reverts commit ee8a720e39ceb7495ab639c1eb6d4987fb6a52bf which got
pushed out despite being nacked.

That commit added a special low-level interface to allow the
crypto_shash API to bypass the safety check for using kernel-mode FPU.
It could give a marginal performance benefit for crypto_shash, but just
is not worth the complexity and footgun.  Moreover, the distinction
between "arch" and "simd" is confusing and is not something that really
should exist in generic code, given that different architectures can
mean different things by "simd".

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 arch/x86/lib/crypto/Kconfig  |  1 -
 arch/x86/lib/crypto/sha256.c | 12 +++---------
 2 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/arch/x86/lib/crypto/Kconfig b/arch/x86/lib/crypto/Kconfig
index 5e94cdee492c2..e344579db3d85 100644
--- a/arch/x86/lib/crypto/Kconfig
+++ b/arch/x86/lib/crypto/Kconfig
@@ -28,7 +28,6 @@ config CRYPTO_POLY1305_X86_64
 config CRYPTO_SHA256_X86_64
 	tristate
 	depends on 64BIT
 	default CRYPTO_LIB_SHA256
 	select CRYPTO_ARCH_HAVE_LIB_SHA256
-	select CRYPTO_ARCH_HAVE_LIB_SHA256_SIMD
 	select CRYPTO_LIB_SHA256_GENERIC
diff --git a/arch/x86/lib/crypto/sha256.c b/arch/x86/lib/crypto/sha256.c
index 80380f8fdcee4..baba74d7d26f2 100644
--- a/arch/x86/lib/crypto/sha256.c
+++ b/arch/x86/lib/crypto/sha256.c
@@ -4,10 +4,11 @@
  *
  * Copyright 2025 Google LLC
  */
 #include <asm/fpu/api.h>
 #include <crypto/internal/sha2.h>
+#include <crypto/internal/simd.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/static_call.h>
 
 asmlinkage void sha256_transform_ssse3(u32 state[SHA256_STATE_WORDS],
@@ -21,28 +22,21 @@ asmlinkage void sha256_ni_transform(u32 state[SHA256_STATE_WORDS],
 
 static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_sha256_x86);
 
 DEFINE_STATIC_CALL(sha256_blocks_x86, sha256_transform_ssse3);
 
-void sha256_blocks_simd(u32 state[SHA256_STATE_WORDS],
+void sha256_blocks_arch(u32 state[SHA256_STATE_WORDS],
 			const u8 *data, size_t nblocks)
 {
-	if (static_branch_likely(&have_sha256_x86)) {
+	if (static_branch_likely(&have_sha256_x86) && crypto_simd_usable()) {
 		kernel_fpu_begin();
 		static_call(sha256_blocks_x86)(state, data, nblocks);
 		kernel_fpu_end();
 	} else {
 		sha256_blocks_generic(state, data, nblocks);
 	}
 }
-EXPORT_SYMBOL_GPL(sha256_blocks_simd);
-
-void sha256_blocks_arch(u32 state[SHA256_STATE_WORDS],
-			const u8 *data, size_t nblocks)
-{
-	sha256_blocks_generic(state, data, nblocks);
-}
 EXPORT_SYMBOL_GPL(sha256_blocks_arch);
 
 bool sha256_is_arch_optimized(void)
 {
 	return static_key_enabled(&have_sha256_x86);
-- 
2.49.0