The patchset can also be retrieved from:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git x86-softirq-fpu-fix-v1
This patchset fixes a longstanding issue where kernel-mode FPU (i.e.,
SIMD) was not reliably usable in softirqs in x86, which was creating the
need for a fallback. The fallback was really bad for performance, and
it even hurt performance for users that never encountered the edge case
where kernel-mode FPU was not usable.
This patchset aligns x86 with other architectures such as arm, arm64,
and riscv by making kernel-mode FPU work in softirqs reliably. There
are a few possible ways to achieve that, and for now I just went with
the simplest way; see patch 1 for details.
Patch 2 eliminates all uses of the "crypto SIMD helper" from x86, as
patch 1 makes it unnecessary. For the RFC it is just one big patch;
I'll probably split patch 2 up if this progresses past RFC status.
Performance results have been positive. All en/decryption is now
slightly faster on x86, as it no longer take a detour through
crypto/simd.c. I get a 7% or 23% improvement for AES-XTS, for example.
I also benchmarked bidirectional IPsec, which has been claimed to often
hit the edge case where kernel-mode FPU was previously not usable in
softirq context. Ultimately, I was not actually able to reproduce that
edge case being reached unless I reduced the number of CPUs to 1, in
which case it then started being occasionally reached. Regardless, even
without that case being reached, IPsec throughput still improved by 2%.
In situations where that case was being reached, or where users required
a synchronous algorithm, a much larger improvement should be seen.
Eric Biggers (2):
x86/fpu: make kernel-mode FPU reliably usable in softirqs
crypto: x86 - stop using the SIMD helper
arch/x86/crypto/Kconfig | 14 --
arch/x86/crypto/aegis128-aesni-glue.c | 13 +-
arch/x86/crypto/aesni-intel_glue.c | 168 ++++++++-------------
arch/x86/crypto/aria_aesni_avx2_glue.c | 22 +--
arch/x86/crypto/aria_aesni_avx_glue.c | 20 +--
arch/x86/crypto/aria_gfni_avx512_glue.c | 22 +--
arch/x86/crypto/camellia_aesni_avx2_glue.c | 21 +--
arch/x86/crypto/camellia_aesni_avx_glue.c | 21 +--
arch/x86/crypto/cast5_avx_glue.c | 21 +--
arch/x86/crypto/cast6_avx_glue.c | 20 +--
arch/x86/crypto/serpent_avx2_glue.c | 21 +--
arch/x86/crypto/serpent_avx_glue.c | 21 +--
arch/x86/crypto/serpent_sse2_glue.c | 21 +--
arch/x86/crypto/sm4_aesni_avx2_glue.c | 30 ++--
arch/x86/crypto/sm4_aesni_avx_glue.c | 30 ++--
arch/x86/crypto/twofish_avx_glue.c | 21 +--
arch/x86/include/asm/fpu/api.h | 17 +--
arch/x86/kernel/fpu/core.c | 37 ++---
18 files changed, 180 insertions(+), 360 deletions(-)
base-commit: 0ad2507d5d93f39619fc42372c347d6006b64319
prerequisite-patch-id: ec1feea7e6f4d03e4e4c64c492197b89c957611a
--
2.48.1
