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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 A085BC43441 for ; Tue, 20 Nov 2018 00:48:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 689B520870 for ; Tue, 20 Nov 2018 00:48:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=sifive.com header.i=@sifive.com header.b="jcHbIDVy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 689B520870 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=sifive.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731969AbeKTLO1 (ORCPT ); Tue, 20 Nov 2018 06:14:27 -0500 Received: from mail-pl1-f196.google.com ([209.85.214.196]:35049 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730335AbeKTLO0 (ORCPT ); Tue, 20 Nov 2018 06:14:26 -0500 Received: by mail-pl1-f196.google.com with SMTP id v1-v6so108298plo.2 for ; Mon, 19 Nov 2018 16:48:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sifive.com; s=google; h=date:subject:in-reply-to:cc:from:to:message-id:mime-version :content-transfer-encoding; bh=gyn6gFow0MKRF0ysKpduDTR/xiD6n6UxxkLJuvi/WtU=; b=jcHbIDVyMH5/sM17UChOWiyCYGg9fqrKV3+Syqz13xN5NHwzJqLmCPCCm1QaPt5Gx2 Lzx8S0bAbR2yJKfgOQb8adRUd3lnS2ZdzL7X+AXsD5MRAi1wiB0EIYpUZPfZ1Pqo8v0Z N4dqEjHE04i9/qEizB2NbEE77BDkxpXwsEWPqCdO1bYBkg7EwSelN+stgHX7CeOeZwOI VF61S5Jk7vKM1UCDAv3px3oWOeXUXkhvmQxEIwsBHgGqSC89O2pq3I31VO8ha7DBbsQ1 SRkZEBTywtzHeCcnf42ka74mbYbv1RrzB+6RVYX/B5DO5ME+Hf9j98q7JJ/JXGpNoS6q FSxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:subject:in-reply-to:cc:from:to:message-id :mime-version:content-transfer-encoding; bh=gyn6gFow0MKRF0ysKpduDTR/xiD6n6UxxkLJuvi/WtU=; b=AsfqBWItxPadMcvOhh8RgGwFRR88LIvJlq/sczevMuHkFQHeQNn2fTxUENTnUaEPzw fYR2/3sec0hwam2IZgjN78HGYXlYoxt8pcM4ziM0aISkQXiNkK1Sd6m2+zXx7BnFQNcI tyskBQbmRlkx57bmWiJR1gdpA8c+yYoI38APhH1LXlMnf1UqWuZaof+gIl5/R7vTab2G RcCJTGYuo3zA3janCOi2hYRFu4XiY7O4OZG99i1em1uIZQJSLtHvsxy4gVMJWk9HZv0r UyJ2fzqZWUX9nDxsKISIdWUoO06gaCdgozlkNCYyMkhRzfyfsYOqYK2I8O9H2bGYmP7z Q1jA== X-Gm-Message-State: AA+aEWaNhrf91Yn0rm+8fg48UA9AOSneLUpJuHPv700qvL99qCYsGY6i YmRhrRcEKk3bwDMK/6Wh0xk4Yg== X-Google-Smtp-Source: AFSGD/UXAP8NEve4cbqy8GP2/ttTy9OfV22j07VMLGvrP06QQe0OH+hpmgegtTOmYWq5skEIjr5dkw== X-Received: by 2002:a17:902:33c2:: with SMTP id b60mr4738641plc.211.1542674883440; Mon, 19 Nov 2018 16:48:03 -0800 (PST) Received: from localhost ([12.206.222.5]) by smtp.gmail.com with ESMTPSA id y29sm48936484pga.59.2018.11.19.16.48.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 19 Nov 2018 16:48:02 -0800 (PST) Date: Mon, 19 Nov 2018 16:48:02 -0800 (PST) X-Google-Original-Date: Mon, 19 Nov 2018 15:54:02 PST (-0800) Subject: Re: [PATCH 2/2] arch: switch the default on ARCH_HAS_SG_CHAIN In-Reply-To: <20181119135852.GA16428@lst.de> CC: Christoph Hellwig , iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org From: Palmer Dabbelt To: Christoph Hellwig Message-ID: Mime-Version: 1.0 (MHng) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 19 Nov 2018 05:58:52 PST (-0800), Christoph Hellwig wrote: > On Fri, Nov 16, 2018 at 08:52:14AM -0800, Palmer Dabbelt wrote: >> As far as I can tell, it looks like m68k, mips, and powerpc mention an >> IOMMU in their ports, don't set ARCH_HAS_SG_CHAIN, and with this patch set >> won't set ARCH_NO_SG_CHAIN. > > m68k has no iommu, and not operations that operate on a scatterlist. > > mips has a trivial iommu driver (jazzdma), but I wrote the current > instance of it, nad it is fine. > > powerpc has various iommu, but actually enables ARCH_HAS_SG_CHAIN > unconditionally. > >> The issue is that I'm not sure how to >> determine what constitutes a horrible legacy IOMMU, at least with respect >> to not being able to use scatterlist chaining. > > It basically means someone is iterating using manual pointer arithmetics > over a multi-element scatterlist instead of using the sg_next and > for_each_sg helpers. Ah, OK. In that case, feel free to drop a Reviewed-by: Palmer Dabbelt in there, if you think it helps any. Thanks for the help!