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=1794430590; b=vJU6ALvoBk+i3fsup1Cys7GvdX0Sk6ZzguS7UqpyH+zQlzIdps27z4AAB9ybPFprjyf5 lWZ2VG1NMZdr+6XAsaZxCrDI5BG4gaVnuwUN5WNLTZ0lVKtQf1na56fQzhuqjTXzI/DsS ayQ/3FXS/TTxzTfObZ3WUkPN0CicOb2YfkKVihynGnQx4F+WyXuljgFmyfE7JUipugyoR i6Jz05jQAyr/YXHLLffJOkEoQkciKZ1pbUeaZkKiiQyTF07plj5IF8McxFpdtLcRhQPMy 2uBDjppNds3BWZMJw+zoswIkCHRBoxrIEaPZsQ7MRBGxJL34CbbEGA4iA7AjahBLivA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794430590; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=pStOyxBQoussPKbDWC0Y4yIvlj83S/Ec9vJBhAymBs8=; b=5F7W+QHwNrtdRGuDvBflM1mn+5rI6jkM6EQ7cs3ihHQXVupEWCbH164ZM1hoy4AmqBrD bjUebpN4T4vjcdIfedpdA9vEL+UpFUgG+GFPR47hYbahiL5QpX5XT+AczWn8hAfXJ5bqO 1UD0Xt8usLs0RAOYYzm93QG/OnsVemahu+cShU/PrnfmxTgKlb31hJZe5agN5wxfVj8u/ ys/ky+vkm7D+MKMQgQKJYaVXkKXopj9BcmoPPrNrNvjqobPSWBsKgjtIQmpcSPMD0Xmri 6xCnm61xJxHmynxP2iIz3wcUYskFVsCq1Sxk3gRXU6kLw7vhCnGSemKgG2H78rZW26Q== 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=YtJF5DBX; 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 E6B67606A32A; Wed, 11 Nov 2026 20:56:29 +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=YtJF5DBX Received: by smtp.kernel.org (Postfix) with ESMTPSA id 397941F00A05; Wed, 11 Nov 2026 20:56:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794430589; bh=pStOyxBQoussPKbDWC0Y4yIvlj83S/Ec9vJBhAymBs8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=YtJF5DBX6JRDTGvLXLB3A1NjGlxPcVZSqlxUGuZfjLGV/gkzTEcD7kRiOt5BmcHOk UD6llHB7uXWkp/KD0rVUqS/sBTPceUz45ulDmOHjJtX7ccbD0eCZPZjtJMd3yTt+u3 SiRi22bj+WhJ/ZSyMRImmmWP4hD6RrpdnY442usSP4AsvAC9tltCDiGeQqL1CrxIny U8ziSRc7T5sgIUTCbm+RdWeT7grjfwIDNKQdp6O/P50t9Y/zyATm6HUnh0UNKqbUPz ZSGg6fT1Yp1vXyjn4koV/x4sVqmAyh6eY8oNX/Z3fg/bLSwsM/yztva9JRV2NLXRaZ elPL/nB9tbcYA== From: Eric Biggers To: akpm@linux-foundation.org, linux-raid@vger.kernel.org Cc: linux-crypto@vger.kernel.org, x86@kernel.org, Christoph Hellwig , Richard Weinberger , Anton Ivanov , Johannes Berg , Eric Biggers Subject: [PATCH 3/3] raid6: opt out of initializing MXCSR and 387 state Date: Wed, 11 Nov 2026 12:56:04 -0800 Message-ID: <20261111205604.47547-4-ebiggers@kernel.org> X-Mailer: git-send-email 2.56.1 In-Reply-To: <20261111205604.47547-1-ebiggers@kernel.org> References: <20261111205604.47547-1-ebiggers@kernel.org> X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The RAID6 code using "kernel-mode FPU" is integer code that does not use any MMX or x87 instructions. (MMX optimized code previously existed but was recently removed.) To the extent that float-domain instructions are used at all, they are only moves, shuffles, and XORs, none 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'. This will make the RAID code consistent with the crypto and CRC code, which are also switching to kernel_fpu_begin_mask(0) (https://lore.kernel.org/linux-crypto/20261105005523.84925-1-ebiggers@kernel.org/). Another 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/raid/raid6/x86/avx2.c | 12 ++++++------ lib/raid/raid6/x86/avx512.c | 12 ++++++------ lib/raid/raid6/x86/recov_avx2.c | 4 ++-- lib/raid/raid6/x86/recov_avx512.c | 4 ++-- lib/raid/raid6/x86/recov_ssse3.c | 4 ++-- lib/raid/raid6/x86/sse2.c | 12 ++++++------ 6 files changed, 24 insertions(+), 24 deletions(-) diff --git a/lib/raid/raid6/x86/avx2.c b/lib/raid/raid6/x86/avx2.c index 3cc2fe7ac42c5..e09d0bd418efc 100644 --- a/lib/raid/raid6/x86/avx2.c +++ b/lib/raid/raid6/x86/avx2.c @@ -32,7 +32,7 @@ static void raid6_avx21_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa %0,%%ymm0" : : "m" (raid6_avx2_constants.x1d[0])); asm volatile("vpxor %ymm3,%ymm3,%ymm3"); /* Zero temp */ @@ -82,7 +82,7 @@ static void raid6_avx21_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa %0,%%ymm0" : : "m" (raid6_avx2_constants.x1d[0])); @@ -139,7 +139,7 @@ static void raid6_avx22_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa %0,%%ymm0" : : "m" (raid6_avx2_constants.x1d[0])); asm volatile("vpxor %ymm1,%ymm1,%ymm1"); /* Zero temp */ @@ -192,7 +192,7 @@ static void raid6_avx22_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa %0,%%ymm0" : : "m" (raid6_avx2_constants.x1d[0])); @@ -271,7 +271,7 @@ static void raid6_avx24_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa %0,%%ymm0" : : "m" (raid6_avx2_constants.x1d[0])); asm volatile("vpxor %ymm1,%ymm1,%ymm1"); /* Zero temp */ @@ -353,7 +353,7 @@ static void raid6_avx24_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa %0,%%ymm0" :: "m" (raid6_avx2_constants.x1d[0])); diff --git a/lib/raid/raid6/x86/avx512.c b/lib/raid/raid6/x86/avx512.c index 772bfc4af6dfd..6ba5ca7df29d5 100644 --- a/lib/raid/raid6/x86/avx512.c +++ b/lib/raid/raid6/x86/avx512.c @@ -34,7 +34,7 @@ static void raid6_avx5121_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa64 %0,%%zmm0\n\t" "vpxorq %%zmm1,%%zmm1,%%zmm1" /* Zero temp */ @@ -93,7 +93,7 @@ static void raid6_avx5121_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa64 %0,%%zmm0" : : "m" (raid6_avx512_constants.x1d[0])); @@ -161,7 +161,7 @@ static void raid6_avx5122_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa64 %0,%%zmm0\n\t" "vpxorq %%zmm1,%%zmm1,%%zmm1" /* Zero temp */ @@ -225,7 +225,7 @@ static void raid6_avx5122_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa64 %0,%%zmm0" : : "m" (raid6_avx512_constants.x1d[0])); @@ -320,7 +320,7 @@ static void raid6_avx5124_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa64 %0,%%zmm0\n\t" "vpxorq %%zmm1,%%zmm1,%%zmm1\n\t" /* Zero temp */ @@ -415,7 +415,7 @@ static void raid6_avx5124_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vmovdqa64 %0,%%zmm0" :: "m" (raid6_avx512_constants.x1d[0])); diff --git a/lib/raid/raid6/x86/recov_avx2.c b/lib/raid/raid6/x86/recov_avx2.c index 820871046e305..41c050746b3dd 100644 --- a/lib/raid/raid6/x86/recov_avx2.c +++ b/lib/raid/raid6/x86/recov_avx2.c @@ -43,7 +43,7 @@ static void raid6_2data_recov_avx2(int disks, size_t bytes, int faila, qmul = raid6_vgfmul[raid6_gfinv[raid6_gfexp[faila] ^ raid6_gfexp[failb]]]; - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); /* ymm0 = x0f[16] */ asm volatile("vpbroadcastb %0, %%ymm7" : : "m" (x0f)); @@ -205,7 +205,7 @@ static void raid6_datap_recov_avx2(int disks, size_t bytes, int faila, /* Now, pick the proper data tables */ qmul = raid6_vgfmul[raid6_gfinv[raid6_gfexp[faila]]]; - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vpbroadcastb %0, %%ymm7" : : "m" (x0f)); diff --git a/lib/raid/raid6/x86/recov_avx512.c b/lib/raid/raid6/x86/recov_avx512.c index 299a3f044d616..3b48822b61ac3 100644 --- a/lib/raid/raid6/x86/recov_avx512.c +++ b/lib/raid/raid6/x86/recov_avx512.c @@ -48,7 +48,7 @@ static void raid6_2data_recov_avx512(int disks, size_t bytes, int faila, qmul = raid6_vgfmul[raid6_gfinv[raid6_gfexp[faila] ^ raid6_gfexp[failb]]]; - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); /* zmm0 = x0f[16] */ asm volatile("vpbroadcastb %0, %%zmm7" : : "m" (x0f)); @@ -243,7 +243,7 @@ static void raid6_datap_recov_avx512(int disks, size_t bytes, int faila, /* Now, pick the proper data tables */ qmul = raid6_vgfmul[raid6_gfinv[raid6_gfexp[faila]]]; - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("vpbroadcastb %0, %%zmm7" : : "m" (x0f)); diff --git a/lib/raid/raid6/x86/recov_ssse3.c b/lib/raid/raid6/x86/recov_ssse3.c index 700bd2c865ece..5540944945d57 100644 --- a/lib/raid/raid6/x86/recov_ssse3.c +++ b/lib/raid/raid6/x86/recov_ssse3.c @@ -44,7 +44,7 @@ static void raid6_2data_recov_ssse3(int disks, size_t bytes, int faila, qmul = raid6_vgfmul[raid6_gfinv[raid6_gfexp[faila] ^ raid6_gfexp[failb]]]; - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("movdqa %0,%%xmm7" : : "m" (x0f[0])); @@ -210,7 +210,7 @@ static void raid6_datap_recov_ssse3(int disks, size_t bytes, int faila, /* Now, pick the proper data tables */ qmul = raid6_vgfmul[raid6_gfinv[raid6_gfexp[faila]]]; - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("movdqa %0, %%xmm7" : : "m" (x0f[0])); diff --git a/lib/raid/raid6/x86/sse2.c b/lib/raid/raid6/x86/sse2.c index 43b09ce58270a..2bbb288c244fc 100644 --- a/lib/raid/raid6/x86/sse2.c +++ b/lib/raid/raid6/x86/sse2.c @@ -28,7 +28,7 @@ static void raid6_sse21_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("movdqa %0,%%xmm0" : : "m" (raid6_sse_constants.x1d[0])); asm volatile("pxor %xmm5,%xmm5"); /* Zero temp */ @@ -80,7 +80,7 @@ static void raid6_sse21_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("movdqa %0,%%xmm0" : : "m" (raid6_sse_constants.x1d[0])); @@ -136,7 +136,7 @@ static void raid6_sse22_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("movdqa %0,%%xmm0" : : "m" (raid6_sse_constants.x1d[0])); asm volatile("pxor %xmm5,%xmm5"); /* Zero temp */ @@ -189,7 +189,7 @@ static void raid6_sse22_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("movdqa %0,%%xmm0" : : "m" (raid6_sse_constants.x1d[0])); @@ -266,7 +266,7 @@ static void raid6_sse24_gen_syndrome(int disks, size_t bytes, void **ptrs) p = dptr[z0+1]; /* XOR parity */ q = dptr[z0+2]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("movdqa %0,%%xmm0" :: "m" (raid6_sse_constants.x1d[0])); asm volatile("pxor %xmm2,%xmm2"); /* P[0] */ @@ -353,7 +353,7 @@ static void raid6_sse24_xor_syndrome(int disks, int start, int stop, p = dptr[disks-2]; /* XOR parity */ q = dptr[disks-1]; /* RS syndrome */ - kernel_fpu_begin(); + kernel_fpu_begin_mask(0); asm volatile("movdqa %0,%%xmm0" :: "m" (raid6_sse_constants.x1d[0])); -- 2.56.1