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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 8BD0DC433E0 for ; Tue, 16 Mar 2021 07:57:09 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 99C1264FE0 for ; Tue, 16 Mar 2021 07:57:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 99C1264FE0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 3C8B84300E; Tue, 16 Mar 2021 07:57:08 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id NOKPuJAN4fYu; Tue, 16 Mar 2021 07:57:07 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp2.osuosl.org (Postfix) with ESMTP id 2A86D43011; Tue, 16 Mar 2021 07:57:07 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id F0CBAC000B; Tue, 16 Mar 2021 07:57:06 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 57D37C000A for ; Tue, 16 Mar 2021 07:57:05 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 379EB4EC2A for ; Tue, 16 Mar 2021 07:57:05 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id v2KYg5U2vv6n for ; Tue, 16 Mar 2021 07:57:04 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by smtp4.osuosl.org (Postfix) with ESMTPS id 241E34EBF8 for ; Tue, 16 Mar 2021 07:57:04 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 7222268C4E; Tue, 16 Mar 2021 08:56:58 +0100 (CET) Date: Tue, 16 Mar 2021 08:56:58 +0100 From: Christoph Hellwig To: Robin Murphy Subject: Re: [RFC PATCH v2 06/11] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg Message-ID: <20210316075658.GA15949@lst.de> References: <20210311233142.7900-1-logang@deltatee.com> <20210311233142.7900-7-logang@deltatee.com> <215e1472-5294-d20a-a43a-ff6dfe8cd66e@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Cc: Minturn Dave B , Jason Gunthorpe , Jakowski Andrzej , linux-pci@vger.kernel.org, Daniel Vetter , Dave Hansen , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Stephen Bates , linux-block@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Christoph Hellwig , Matthew Wilcox , Jason Ekstrand , John Hubbard , Dan Williams , Logan Gunthorpe , Christian =?iso-8859-1?Q?K=F6nig?= , Xiong Jianxin X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Fri, Mar 12, 2021 at 06:11:17PM +0000, Robin Murphy wrote: > Sure, that's how things stand immediately after this patch. But then > someone comes along with the perfectly reasonable argument for returning > more expressive error information for regular mapping failures as well > (because sometimes those can be terminal too, as above), we start to get > divergent behaviour across architectures and random bits of old code subtly > breaking down the line. *That* is what makes me wary of making a > fundamental change to a long-standing "nonzero means success" interface... Agreed. IMHO dma_map_sg actually needs to be switched to return unsigned to help root this out, going the other way is no helpful. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu