Date: Sat, 20 Oct 2012 11:10:37 -0700 From: Peter Wemm <peter@wemm.org> To: Konstantin Belousov <kostikbel@gmail.com>, freebsd-arch@freebsd.org Subject: Re: using SSE2 in kernel C code (improving AES-NI module) Message-ID: <CAGE5yCoM92rU7Ca7C7_x=3vXW%2BqO9Zc0uQhPURuMbstPDvq9yg@mail.gmail.com> In-Reply-To: <20121020171124.GU1967@funkthat.com> References: <20121019233833.GS1967@funkthat.com> <20121020054847.GB35915@deviant.kiev.zoral.com.ua> <20121020171124.GU1967@funkthat.com>
next in thread | previous in thread | raw e-mail | index | archive | help
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. 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAGE5yCoM92rU7Ca7C7_x=3vXW%2BqO9Zc0uQhPURuMbstPDvq9yg>