From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F8CCC433E1 for ; Wed, 15 Jul 2020 17:56:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 019B920663 for ; Wed, 15 Jul 2020 17:56:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Yo/iLTkC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726898AbgGOR4Y (ORCPT ); Wed, 15 Jul 2020 13:56:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725882AbgGOR4U (ORCPT ); Wed, 15 Jul 2020 13:56:20 -0400 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1EF8AC061755; Wed, 15 Jul 2020 10:56:20 -0700 (PDT) Received: by mail-wr1-x442.google.com with SMTP id f2so3658681wrp.7; Wed, 15 Jul 2020 10:56:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=txrkPrZiEn1pbT9kzdmetNqwIC2PvBGCwV/yJihymvQ=; b=Yo/iLTkCOqUsykROi54kl7CXKAvBJVM2tFfbAhRX6TsblZCX1MJMyvsJbGn/NkBDzC KCnCXJ5z+Tyhy4z2tC+xHjEouoz2j3ja0nn/o7PJhs4U2OilX6G8RW82mNk/g+0JLzFI cAB9eabMoNyIpuwspNK7eEbw9oxRpVXgGwLs9YnQRQ8fcuhKhGmCqUjkqv84V00u/BKv 9S+a/zpoyykQ6RlHPPoNe8fckniBZpWZtSm1Lm+Mg4qJMRWP9nDnp/acCVZRrYml3EVE xXcIp1cJet4qX3zvzmHXDDGSfkQcwKb59CVUwWpepUhoB3ACIQ9/N8UazhKz4FpCH/XJ f4uQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=txrkPrZiEn1pbT9kzdmetNqwIC2PvBGCwV/yJihymvQ=; b=a91XXjrWXj+72Sz9tv/5hRLXcIL6slpZ9gtqCi1DuXzPmDN+Z6eki+5XL07gMBunyN UgeVU+EUnl07jfwbjehPotrocKbmdc7PfYxgZ/BdLagQxZnTGRq+LunSW97TaFvdC5SC 6L/LxY4S7L0BaQgXCj9fKqNm9BfqXH07n2/SpiXB/QQdQ42Njen1S/P9lZHAvA9I5zaP ++UFoa4j48I5e5DKT+/NBcqsCo05C2qaOYRDzPB4KOzdEh1HmKztvj9TaRYe/eckRkJ7 NU9hOSSNfNEQOlXuXt0u82Xp5UB3Y7f7UbY87+B3YAMnX0PSa5fUy84m8NdQ+s64wMN+ 2uAw== X-Gm-Message-State: AOAM532SR5rjfYjHtKyxDxNAouXIbj9H1epPLxlVrHZJDf4ceky47fT8 IeEOGYiWYNAr+BeyIQt0MHlWQ6v+JuVnOkcMLww= X-Google-Smtp-Source: ABdhPJwKTDDMyra+aSCx70aaxxEryoqGVH2kq/Vy70Lnm2CkKYtD0NcGtJo864aQiOBDMkj1VN7eSL+yNdnVk5jeG8k= X-Received: by 2002:adf:82b8:: with SMTP id 53mr614398wrc.172.1594835778778; Wed, 15 Jul 2020 10:56:18 -0700 (PDT) MIME-Version: 1.0 References: <20200713183711.762244-1-luke.r.nels@gmail.com> In-Reply-To: <20200713183711.762244-1-luke.r.nels@gmail.com> From: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= Date: Wed, 15 Jul 2020 19:56:06 +0200 Message-ID: Subject: Re: [RFC PATCH bpf-next 0/3] bpf, riscv: Add compressed instructions to rv64 JIT To: Luke Nelson Cc: bpf , Luke Nelson , Xi Wang , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , John Fastabend , KP Singh , Netdev , linux-riscv , LKML Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 13 Jul 2020 at 20:37, Luke Nelson wrot= e: > > This patch series enables using compressed riscv (RVC) instructions > in the rv64 BPF JIT. > First of all; Really nice work. I like this, and it makes the code easier to read as well (e.g. emit_mv). I'm a bit curious why you only did it for RV64, and not RV32? I have some minor comments on the patches. I strongly encourage you to submit this as a proper (non-RFC) set for bpf-next. Cheers, Bj=C3=B6rn > RVC is a standard riscv extension that adds a set of compressed, > 2-byte instructions that can replace some regular 4-byte instructions > for improved code density. > > This series first modifies the JIT to support using 2-byte instructions > (e.g., in jump offset computations), then adds RVC encoding and > helper functions, and finally uses the helper functions to optimize > the rv64 JIT. > > I used our formal verification framework, Serval, to verify the > correctness of the RVC encodings and their uses in the rv64 JIT. > > The JIT continues to pass all tests in lib/test_bpf.c, and introduces > no new failures to test_verifier; both with and without RVC being enabled= . > > The following are examples of the JITed code for the verifier selftest > "direct packet read test#3 for CGROUP_SKB OK", without and with RVC > enabled, respectively. The former uses 178 bytes, and the latter uses 112= , > for a ~37% reduction in code size for this example. > > Without RVC: > > 0: 02000813 addi a6,zero,32 > 4: fd010113 addi sp,sp,-48 > 8: 02813423 sd s0,40(sp) > c: 02913023 sd s1,32(sp) > 10: 01213c23 sd s2,24(sp) > 14: 01313823 sd s3,16(sp) > 18: 01413423 sd s4,8(sp) > 1c: 03010413 addi s0,sp,48 > 20: 03056683 lwu a3,48(a0) > 24: 02069693 slli a3,a3,0x20 > 28: 0206d693 srli a3,a3,0x20 > 2c: 03456703 lwu a4,52(a0) > 30: 02071713 slli a4,a4,0x20 > 34: 02075713 srli a4,a4,0x20 > 38: 03856483 lwu s1,56(a0) > 3c: 02049493 slli s1,s1,0x20 > 40: 0204d493 srli s1,s1,0x20 > 44: 03c56903 lwu s2,60(a0) > 48: 02091913 slli s2,s2,0x20 > 4c: 02095913 srli s2,s2,0x20 > 50: 04056983 lwu s3,64(a0) > 54: 02099993 slli s3,s3,0x20 > 58: 0209d993 srli s3,s3,0x20 > 5c: 09056a03 lwu s4,144(a0) > 60: 020a1a13 slli s4,s4,0x20 > 64: 020a5a13 srli s4,s4,0x20 > 68: 00900313 addi t1,zero,9 > 6c: 006a7463 bgeu s4,t1,0x74 > 70: 00000a13 addi s4,zero,0 > 74: 02d52823 sw a3,48(a0) > 78: 02e52a23 sw a4,52(a0) > 7c: 02952c23 sw s1,56(a0) > 80: 03252e23 sw s2,60(a0) > 84: 05352023 sw s3,64(a0) > 88: 00000793 addi a5,zero,0 > 8c: 02813403 ld s0,40(sp) > 90: 02013483 ld s1,32(sp) > 94: 01813903 ld s2,24(sp) > 98: 01013983 ld s3,16(sp) > 9c: 00813a03 ld s4,8(sp) > a0: 03010113 addi sp,sp,48 > a4: 00078513 addi a0,a5,0 > a8: 00008067 jalr zero,0(ra) > > With RVC: > > 0: 02000813 addi a6,zero,32 > 4: 7179 c.addi16sp sp,-48 > 6: f422 c.sdsp s0,40(sp) > 8: f026 c.sdsp s1,32(sp) > a: ec4a c.sdsp s2,24(sp) > c: e84e c.sdsp s3,16(sp) > e: e452 c.sdsp s4,8(sp) > 10: 1800 c.addi4spn s0,sp,48 > 12: 03056683 lwu a3,48(a0) > 16: 1682 c.slli a3,0x20 > 18: 9281 c.srli a3,0x20 > 1a: 03456703 lwu a4,52(a0) > 1e: 1702 c.slli a4,0x20 > 20: 9301 c.srli a4,0x20 > 22: 03856483 lwu s1,56(a0) > 26: 1482 c.slli s1,0x20 > 28: 9081 c.srli s1,0x20 > 2a: 03c56903 lwu s2,60(a0) > 2e: 1902 c.slli s2,0x20 > 30: 02095913 srli s2,s2,0x20 > 34: 04056983 lwu s3,64(a0) > 38: 1982 c.slli s3,0x20 > 3a: 0209d993 srli s3,s3,0x20 > 3e: 09056a03 lwu s4,144(a0) > 42: 1a02 c.slli s4,0x20 > 44: 020a5a13 srli s4,s4,0x20 > 48: 4325 c.li t1,9 > 4a: 006a7363 bgeu s4,t1,0x50 > 4e: 4a01 c.li s4,0 > 50: d914 c.sw a3,48(a0) > 52: d958 c.sw a4,52(a0) > 54: dd04 c.sw s1,56(a0) > 56: 03252e23 sw s2,60(a0) > 5a: 05352023 sw s3,64(a0) > 5e: 4781 c.li a5,0 > 60: 7422 c.ldsp s0,40(sp) > 62: 7482 c.ldsp s1,32(sp) > 64: 6962 c.ldsp s2,24(sp) > 66: 69c2 c.ldsp s3,16(sp) > 68: 6a22 c.ldsp s4,8(sp) > 6a: 6145 c.addi16sp sp,48 > 6c: 853e c.mv a0,a5 > 6e: 8082 c.jr ra > > Luke Nelson (3): > bpf, riscv: Modify JIT ctx to support compressed instructions > bpf, riscv: Add encodings for compressed instructions > bpf, riscv: Use compressed instructions in the rv64 JIT > > arch/riscv/net/bpf_jit.h | 495 +++++++++++++++++++++++++++++++- > arch/riscv/net/bpf_jit_comp32.c | 14 +- > arch/riscv/net/bpf_jit_comp64.c | 287 +++++++++--------- > arch/riscv/net/bpf_jit_core.c | 6 +- > 4 files changed, 650 insertions(+), 152 deletions(-) > > -- > 2.25.1 >