From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794088564; b=nDHyHPeiARDhGO1Czham3n+v6uPzKyauG2yN6ah90AqNKTKBm/ARsUgUshpwx5R3qS7v YPR1p67gTVVcFur4CKOmuYX8EewZKeAID3/F6Jouln9DM8HvJ/qIr710piO2yflAwRjps /4HJNVJ85+1hg6I4zRXmBdbBA32GR888Zgs7QLr11yfHBT2yasHKOv4ffTl2EUVLl5Rh0 4hiftOVv/K9HWDfZoYkvOtwltodb2jFFQ2XHy9THs936dC/Zc4TwV5W3jwK4hHwyy7eVs hMtTZjxmP0n58AWsi52vEGaVZnGzZsYJOH9xyQq7ik4iU2dregILsoySihk9d6nlefg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794088564; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=GAXt+gB49McI0nwQHHJW1Y2EfO3QNGnxsgrwkzL5pHU=; b=i7MfDiD6hfdNURAfcmqkAXVmVUIQeQ+q0ex1DirIZ1PnHsoUp5jRQXpl90inZYt/5KXX nWCDXqihmie1h06OLzuLsW8CdXl5TVx4Ivr+96ffisndzgHnFN4XNZJt2oeG8zZXkce1Z s9ZBdXs9JhdmI52UnYpcIWhonP1z88v2o+4/SL2ywWcqbM0i06ApotvB01MQHXgvvOmgm DSwN3+PNZJ8qKUdzIU7SEF4JzRhjbP5w6xsqZwIZyP5o7xJYxJAWRdT+0eVCYX+8Le9WD /hnIPFvSIUC8/QoCR/2XlfVKtvw37Hq/FgVQTFol6MiQHFTV912vvyPI3aNwq/OudNQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=C3gQeTGQ; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 68C0C606A326 for ; Sat, 7 Nov 2026 21:56:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=C3gQeTGQ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 930901F0089F; Sat, 7 Nov 2026 21:56:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794088564; bh=GAXt+gB49McI0nwQHHJW1Y2EfO3QNGnxsgrwkzL5pHU=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=C3gQeTGQmKhTRlrxYh8mCqOy41Gb5th4byfvnkEA4tNnS/580WA4Dp5psr8Fi80dA Goa0YUDIx6nMquuDu91b1HKB189NQXrOPPhIQd67iN7YaCF5mxWqyvZzKBaiysO9bX oR9E9NZcJDLZNHIGAqI72FSwOj/ADqURJybgQacZfbSQX56SlZtmK9XEubTqtF0gkg yfn5nqMYtiHTyV+mTmmBlPofixktq9V5XmMXIXSbu4ntdDPOcLSBAKVhLiPtNzIFbK uuqxhE7Ot5Aa661MZon4x+OzVq2OgQRohmMbh/8JOhsNe0Q2p0LyM1BOfL3UAkrQeY fcua0xBqrTRvg== Date: Sat, 7 Nov 2026 13:56:02 -0800 From: Eric Biggers To: linux-crypto@vger.kernel.org Cc: Ard Biesheuvel , "Jason A . Donenfeld" , Herbert Xu , x86@kernel.org Subject: Re: [PATCH 2/3] lib/crypto: x86: Opt out of initializing MXCSR and 387 state Message-ID: <20261107215602.GJ137269@quark> References: <20261105005523.84925-1-ebiggers@kernel.org> <20261105005523.84925-3-ebiggers@kernel.org> X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261105005523.84925-3-ebiggers@kernel.org> On Wed, Nov 04, 2026 at 04:55:22PM -0800, Eric Biggers wrote: > The crypto code using "kernel-mode FPU" is integer code that does not > use any MMX or x87 instructions. To the extent that float-domain > instructions are used at all, they are only moves and shuffles, neither > of which raises SIMD floating-point exceptions or depends on MXCSR. > > Therefore, there's no need to initialize MXCSR or the 387 FPU state. > > Opt out of this initialization by using kernel_fpu_begin_mask(0) instead > of kernel_fpu_begin(). This eliminates an 'ldmxcsr' instruction in > every kernel-mode FPU section, reducing overhead, which matters most for > short input lengths. On 32-bit kernels it also eliminates 'fninit'. > > A precedent for this optimization can be found in > commit a58db7ad80e8 ("netfilter: nft_set_pipapo_avx2: Skip LDMXCSR, we > don't need a valid MXCSR state"). > > Signed-off-by: Eric Biggers > --- > lib/crypto/x86/aes.h | 24 ++++++++++++------------ > lib/crypto/x86/blake2s.h | 2 +- > lib/crypto/x86/chacha.h | 4 ++-- > lib/crypto/x86/gf128hash.h | 8 ++++---- > lib/crypto/x86/nh.h | 2 +- > lib/crypto/x86/poly1305.h | 2 +- > lib/crypto/x86/sha1.h | 4 ++-- > lib/crypto/x86/sha256.h | 4 ++-- > lib/crypto/x86/sha512.h | 2 +- > lib/crypto/x86/sm3.h | 2 +- > 10 files changed, 27 insertions(+), 27 deletions(-) Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-next Reviews and acks appreciated! - Eric