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=-2.2 required=3.0 tests=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 5CE06C4CEC4 for ; Mon, 23 Sep 2019 15:21:54 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (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 3916520820 for ; Mon, 23 Sep 2019 15:21:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3916520820 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 mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id A239EDA8; Mon, 23 Sep 2019 15:21:24 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 9F92CDA2 for ; Mon, 23 Sep 2019 15:21:22 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 1008A8A0 for ; Mon, 23 Sep 2019 15:21:21 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 8CFCD227A81; Mon, 23 Sep 2019 17:21:17 +0200 (CEST) Date: Mon, 23 Sep 2019 17:21:17 +0200 From: Christoph Hellwig To: Halil Pasic Subject: Re: [RFC PATCH 1/3] dma-mapping: make overriding GFP_* flags arch customizable Message-ID: <20190923152117.GA2767@lst.de> References: <20190923123418.22695-1-pasic@linux.ibm.com> <20190923123418.22695-2-pasic@linux.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190923123418.22695-2-pasic@linux.ibm.com> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: linux-s390@vger.kernel.org, Janosch Frank , Vasily Gorbik , Cornelia Huck , Heiko Carstens , Peter Oberparleiter , linux-kernel@vger.kernel.org, Christian Borntraeger , iommu@lists.linux-foundation.org, Christoph Hellwig , Gerald Schaefer X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 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 Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Mon, Sep 23, 2019 at 02:34:16PM +0200, Halil Pasic wrote: > Before commit 57bf5a8963f8 ("dma-mapping: clear harmful GFP_* flags in > common code") tweaking the client code supplied GFP_* flags used to be > an issue handled in the architecture specific code. The commit message > suggests, that fixing the client code would actually be a better way > of dealing with this. > > On s390 common I/O devices are generally capable of using the full 64 > bit address space for DMA I/O, but some chunks of the DMA memory need to > be 31 bit addressable (in physical address space) because the > instructions involved mandate it. Before switching to DMA API this used > to be a non-issue, we used to allocate those chunks from ZONE_DMA. > Currently our only option with the DMA API is to restrict the devices to > (via dma_mask and dma_mask_coherent) to 31 bit, which is sub-optimal. > > Thus s390 we would benefit form having control over what flags are > dropped. No way, sorry. You need to express that using a dma mask instead of overloading the GFP flags. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu