linux-kernel - [PATCH 09/12] lib/crypto: blake2s: Always enable arch-optimized BLAKE2s code

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Message-ID: <20250827151131.27733-10-ebiggers@kernel.org>
Date: Wed, 27 Aug 2025 08:11:28 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: linux-crypto@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Ard Biesheuvel <ardb@...nel.org>,
	"Jason A . Donenfeld" <Jason@...c4.com>,
	x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	Eric Biggers <ebiggers@...nel.org>
Subject: [PATCH 09/12] lib/crypto: blake2s: Always enable arch-optimized BLAKE2s code

When support for a crypto algorithm is enabled, the arch-optimized
implementation of that algorithm should be enabled too.  We've learned
this the hard way many times over the years: people regularly forget to
enable the arch-optimized implementations of the crypto algorithms,
resulting in significant performance being left on the table.

Currently, BLAKE2s support is always enabled ('obj-y'), since random.c
uses it.  Therefore, the arch-optimized BLAKE2s code, which exists for
ARM and x86_64, should be always enabled too.  Let's do that.

Note that the effect on kernel image size is very small and should not
be a concern.  On ARM, enabling CRYPTO_BLAKE2S_ARM actually *shrinks*
the kernel size by about 1200 bytes, since the ARM-optimized
blake2s_compress() completely replaces the generic blake2s_compress().
On x86_64, enabling CRYPTO_BLAKE2S_X86 increases the kernel size by
about 1400 bytes, as the generic blake2s_compress() is still included as
a fallback; however, for context, that is only about a quarter the size
of the generic blake2s_compress().  The x86_64 optimized BLAKE2s code
uses much less icache at runtime than the generic code.

Signed-off-by: Eric Biggers <ebiggers@...nel.org>
---
 lib/crypto/arm/Kconfig | 2 +-
 lib/crypto/x86/Kconfig | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/crypto/arm/Kconfig b/lib/crypto/arm/Kconfig
index 740341aa35d21..a5607ad079c4f 100644
--- a/lib/crypto/arm/Kconfig
+++ b/lib/crypto/arm/Kconfig
@@ -1,9 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0-only

 config CRYPTO_BLAKE2S_ARM
-	bool "Hash functions: BLAKE2s"
+	def_bool y
 	select CRYPTO_ARCH_HAVE_LIB_BLAKE2S
 	help
 	  BLAKE2s cryptographic hash function (RFC 7693)

 	  Architecture: arm
diff --git a/lib/crypto/x86/Kconfig b/lib/crypto/x86/Kconfig
index eb47da71aa6b6..ffa718321369f 100644
--- a/lib/crypto/x86/Kconfig
+++ b/lib/crypto/x86/Kconfig
@@ -1,9 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0-only

 config CRYPTO_BLAKE2S_X86
-	bool "Hash functions: BLAKE2s (SSSE3/AVX-512)"
+	def_bool y
 	depends on 64BIT
 	select CRYPTO_LIB_BLAKE2S_GENERIC
 	select CRYPTO_ARCH_HAVE_LIB_BLAKE2S
 	help
 	  BLAKE2s cryptographic hash function (RFC 7693)
-- 
2.50.1