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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 4B739C282DD for ; Wed, 22 May 2019 12:33:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 282352173C for ; Wed, 22 May 2019 12:33:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729386AbfEVMdI (ORCPT ); Wed, 22 May 2019 08:33:08 -0400 Received: from verein.lst.de ([213.95.11.211]:39305 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728914AbfEVMdH (ORCPT ); Wed, 22 May 2019 08:33:07 -0400 Received: by newverein.lst.de (Postfix, from userid 2407) id 25DE967358; Wed, 22 May 2019 14:32:44 +0200 (CEST) Date: Wed, 22 May 2019 14:32:43 +0200 From: Christoph Hellwig To: Horia =?utf-8?Q?Geant=C4=83?= Cc: Konrad Rzeszutek Wilk , Christoph Hellwig , Marek Szyprowski , Robin Murphy , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-imx@nxp.com Subject: Re: [PATCH] swiotlb: sync buffer when mapping FROM_DEVICE Message-ID: <20190522123243.GA26390@lst.de> References: <20190522072018.10660-1-horia.geanta@nxp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190522072018.10660-1-horia.geanta@nxp.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I'm a little worried about this. While it looks functionally correct we have surived without it, and doing another copy for every swiotlb dma mapping from the device looks extremely painful for the typical use cases where we expect the device to transfer the whole mapping. I'd be tempted to instead properl document the current behavior and introduce a new DMA_ATTR_PARTIAL flag to allow for partial mappings.