From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by kanga.kvack.org (Postfix) with ESMTP id 17D0A6B4ED5 for ; Wed, 28 Nov 2018 15:35:15 -0500 (EST) Received: by mail-pf1-f199.google.com with SMTP id v79so17769465pfd.20 for ; Wed, 28 Nov 2018 12:35:15 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id w12si8988377pfn.212.2018.11.28.12.35.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 28 Nov 2018 12:35:13 -0800 (PST) Date: Wed, 28 Nov 2018 21:35:10 +0100 From: Michal =?UTF-8?B?U3VjaMOhbmVr?= Subject: Re: use generic DMA mapping code in powerpc V4 Message-ID: <20181128213510.543259e3@kitsune.suse.cz> In-Reply-To: <535776df-dea3-eb26-6bf3-83f225e977df@xenosoft.de> References: <20181114082314.8965-1-hch@lst.de> <20181127074253.GB30186@lst.de> <87zhttfonk.fsf@concordia.ellerman.id.au> <535776df-dea3-eb26-6bf3-83f225e977df@xenosoft.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christian Zigotzky Cc: Michael Ellerman , Christoph Hellwig , Benjamin Herrenschmidt , Paul Mackerras , linux-arch@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org On Wed, 28 Nov 2018 16:55:30 +0100 Christian Zigotzky wrote: > On 28 November 2018 at 12:05PM, Michael Ellerman wrote: > > Nothing specific yet. > > > > I'm a bit worried it might break one of the many old obscure platforms > > we have that aren't well tested. > > > Please don't apply the new DMA mapping code if you don't be sure if it > works on all supported PowerPC machines. Is the new DMA mapping code > really necessary? It's not really nice, to rewrote code if the old code > works perfect. We must not forget, that we work for the end users. Does > the end user have advantages with this new code? Is it faster? The old > code works without any problems. There is another service provided to the users as well: new code that is cleaner and simpler which allows easier bug fixes and new features. Without being familiar with the DMA mapping code I cannot really say if that's the case here. > I am also worried about this code. How > can I test this new DMA mapping code? I suppose if your machine works it works for you. Thanks Michal