Date: Sat, 20 Oct 2012 21:18:26 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Peter Wemm <peter@wemm.org> Cc: freebsd-arch@freebsd.org Subject: Re: using SSE2 in kernel C code (improving AES-NI module) Message-ID: <20121020181826.GE35915@deviant.kiev.zoral.com.ua> In-Reply-To: <CAGE5yCoM92rU7Ca7C7_x=3vXW%2BqO9Zc0uQhPURuMbstPDvq9yg@mail.gmail.com> References: <20121019233833.GS1967@funkthat.com> <20121020054847.GB35915@deviant.kiev.zoral.com.ua> <20121020171124.GU1967@funkthat.com> <CAGE5yCoM92rU7Ca7C7_x=3vXW%2BqO9Zc0uQhPURuMbstPDvq9yg@mail.gmail.com>
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[-- Attachment #1 --] On Sat, Oct 20, 2012 at 11:10:37AM -0700, Peter Wemm wrote: > On Sat, Oct 20, 2012 at 10:11 AM, John-Mark Gurney <jmg@funkthat.com> wrote: > > Konstantin Belousov wrote this message on Sat, Oct 20, 2012 at 08:48 +0300: > >> On Fri, Oct 19, 2012 at 04:38:33PM -0700, John-Mark Gurney wrote: > >> > So, the AES-NI module already uses SSE2 instructions, but it does so > >> > only in assembly. I have improved the performance of the AES-NI > >> > modules implementation, but this involves me using additional SSE2 > >> > instructions. > >> > > >> > In order to keep my sanity, I did part of the new code in C using > >> > gcc native types and xmmintrin.h, but we do not support this header in > >> > the kernel.. This means we cannot simply add the new code to the > >> > kernel... > >> > > >> > Any good ideas on how to integrate this code into the kernel build? > > > > [...] > > > >> > >> The current structure of the aes-ni driver is partly enforced by the > >> issue you noted. We cannot use sse intristics in the kernel, and > >> huge inline assembler fragments are hard to write. > >> > >> I prefer to have the separate .S files with the optimized code, > >> hand-written. If needed, I offer you a help with transition. I would > >> need a full patch to rewrite the code. > > > > Are you sure you want to do this? It'll involve writing around 500 > > lines of assembly besides the constants... And it isn't simple like > > the aesni_enc where we have a single loop for the rounds... I've > > posted a tar.gz to overlay onto sys/crypto/aesni at: > > https://www.funkthat.com/~jmg/aesni.repfile.tar.gz > > Rather than go straight to assembler, why not use the __builtins? > > static inline __m128i > xts_crank_lfsr(__m128i inp) > { > const __m128i alphamask = _mm_set_epi32(1, 1, 1, AES_XTS_ALPHA); > __m128i xtweak, ret; > > /* set up xor mask */ > xtweak = _mm_shuffle_epi32(inp, 0x93); > xtweak = _mm_srai_epi32(xtweak, 31); > xtweak &= alphamask; > > /* next term */ > ret = _mm_slli_epi32(inp, 1); > ret ^= xtweak; > > return ret; > } > > --> > > static inline __m128i > xts_crank_lfsr(__m128i inp) > { > const __m128i alphamask = (magic casts){ 1, 1, 1, AES_XTS_ALPHA }; > __m128i xtweak, ret; > > /* set up xor mask */ > xtweak = __builtin_ia32_pshufd (inp, 0x93); > xtweak = __builtin_ia32_psradi128(xtweak, 31); > xtweak &= alphamask; > > /* next term */ > ret = __builtin_ia32_pslldi128(inp, 1); > ret ^= xtweak; > > return ret; > } > I know I skipped the details like data types, but most of the meat of > those functions collapses to a simple wrapper around a __builtin. Are builtins available for -mno-sse compilation ? I think we can try to reimplement the builtins needed with inline assembly. > > Or, another option.. do something like genassym or the many other > kernel build tools. aicasm builds and runs a userland tool to > generate something to build into the kernel. With sufficient > cross-contamination safeguards I wonder if something similar might be > able to be done here. > > -- > Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV > "All of this is for nothing if we don't go to the stars" - JMS/B5 > "If Java had true garbage collection, most programs would delete > themselves upon execution." -- Robert Sewell [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAlCC6vIACgkQC3+MBN1Mb4hAjQCgz1gcbmOjWckG3SoEdiu+iI5G tS0An0idGjpvu5as8W3w9dz9EENqcrFd =RfrP -----END PGP SIGNATURE-----home | help
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