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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 A04D5C43603 for ; Fri, 6 Dec 2019 08:11:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 704372466E for ; Fri, 6 Dec 2019 08:11:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=dlink.ru header.i=@dlink.ru header.b="nrDzP7yd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726423AbfLFILy (ORCPT ); Fri, 6 Dec 2019 03:11:54 -0500 Received: from mail.dlink.ru ([178.170.168.18]:47228 "EHLO fd.dlink.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726350AbfLFILy (ORCPT ); Fri, 6 Dec 2019 03:11:54 -0500 Received: by fd.dlink.ru (Postfix, from userid 5000) id D4A7B1B20153; Fri, 6 Dec 2019 11:11:49 +0300 (MSK) DKIM-Filter: OpenDKIM Filter v2.11.0 fd.dlink.ru D4A7B1B20153 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=dlink.ru; s=mail; t=1575619910; bh=za+GdP4j4RE1pd9atrwIHfrHFE+ujrS1ZdTfSPyF48Q=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=nrDzP7yd6HXSc1LtC8Gjwu8u+3kzSGnBldhMKb0ZZBXrSgaTE+SLavTEnnumW08b0 HJ+PIXJJ7xvJsunyP4ArMuH2xlHoUKlLkbv9HpFrWofYFK//0PsHzgDu/1esHI4rqP YB9b+PTcGB5kVqh+OhS1RLgR/zaHOeDwGLGOTwe0= Received: from mail.rzn.dlink.ru (mail.rzn.dlink.ru [178.170.168.13]) by fd.dlink.ru (Postfix) with ESMTP id 6B7ED1B20153; Fri, 6 Dec 2019 11:11:41 +0300 (MSK) DKIM-Filter: OpenDKIM Filter v2.11.0 fd.dlink.ru 6B7ED1B20153 Received: from mail.rzn.dlink.ru (localhost [127.0.0.1]) by mail.rzn.dlink.ru (Postfix) with ESMTP id D1A151B22664; Fri, 6 Dec 2019 11:11:40 +0300 (MSK) Received: from mail.rzn.dlink.ru (localhost [127.0.0.1]) by mail.rzn.dlink.ru (Postfix) with ESMTPA; Fri, 6 Dec 2019 11:11:40 +0300 (MSK) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Fri, 06 Dec 2019 11:11:40 +0300 From: Alexander Lobakin To: Paul Burton Cc: Paul Burton , Hassan Naveed , Ralf Baechle , James Hogan , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: MIPS eBPF JIT support on pre-32R2 In-Reply-To: <647fa62c7111a27a2cc217cf06cbe355@dlink.ru> References: <09d713a59665d745e21d021deeaebe0a@dlink.ru> <20191205184450.lbrkenmursz4zpdm@lantea.localdomain> <647fa62c7111a27a2cc217cf06cbe355@dlink.ru> User-Agent: Roundcube Webmail/1.4.0 Message-ID: X-Sender: alobakin@dlink.ru Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Alexander Lobakin писал 06.12.2019 10:20: > Paul Burton wrote 05.12.2019 21:44: >> Hi Alexander, > > Hi Paul! > >> On Thu, Dec 05, 2019 at 03:45:27PM +0300, Alexander Lobakin wrote: >>> Hey all, >>> >>> I'm writing about lines arch/mips/net/ebpf_jit.c:1806-1807: >>> >>> if (!prog->jit_requested || MIPS_ISA_REV < 2) >>> return prog; >>> >>> Do pre-32R2 architectures (32R1, maybe even R3000-like) actually >>> support >>> this eBPF JIT code? >> >> No, they don't; the eBPF JIT makes unconditional use of at least the >> (d)ins & (d)ext instructions which were added in MIPSr2, so it would >> result in reserved instruction exceptions & panics if enabled on >> pre-MIPSr2 CPUs. >> >>> If they do, then the condition 'MIPS_ISA_REV < 2' >>> should be removed as it is always true for them and tells CC to >>> remove >>> JIT completely. >>> >>> If they don't support instructions from this JIT, then the line >>> arch/mips/Kconfig:50: >>> >>> select HAVE_EBPF_JIT if (!CPU_MICROMIPS) >>> >>> should be changed to something like: >>> >>> select HAVE_EBPF_JIT if !CPU_MICROMIPS && TARGET_ISA_REV >= 2 >>> >>> (and then the mentioned 'if' condition would become redundant) >> >> Good spot; I agree entirely, this dependency should be reflected in >> Kconfig. >> >>> At the moment it is possible to build a kernel without both JIT and >>> interpreter, but with CONFIG_BPF_SYSCALL=y (what should not be >>> allowed >>> I suppose?) within the following configuration: >>> >>> - select any pre-32R2 CPU (e.g. CONFIG_CPU_MIPS32_R1); >>> - enable CONFIG_BPF_JIT (CONFIG_MIPS_EBPF_JIT will be autoselected); >>> - enable CONFIG_BPF_JIT_ALWAYS_ON (this removes BPF interpreter from >>> the system). >>> >>> I may prepare a proper patch by myself if needed (after >>> clarification). >> >> That would be great, thanks! > > Great, I'll send it in about ~2-3 hours. Here we are: [1] Yep, this will conflict with your patch restoring cBPF for MIPS32. If you have any questions about my patch or I should change anything in it, please let me know. Thanks! >> One thing to note is that I hope we'll restore the cBPF JIT with this >> patch: >> >> https://lore.kernel.org/linux-mips/20191205182318.2761605-1-paulburton@kernel.org/T/#u >> >> The cBPF JIT looks like it should work on older pre-MIPSr2 CPUs, so >> the >> only way this is relevant is that your patch might have a minor >> conflict. But I thought I'd mention it anyway :) > > Yes, I thought about this too. If pre-32R2 CPUs don't support our eBPF > JIT, we'd better restore cBPF for them, so they could speed-up at least > "classic" instructions. Glad you've decided to do that. > >> Thanks, >> Paul > > Regards, > ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ [1] https://lore.kernel.org/linux-mips/20191206080741.12306-1-alobakin@dlink.ru/ Regards, ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ