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[209.132.180.67]) by mx.google.com with ESMTP id 3-v6si1504078plr.440.2018.04.27.09.37.32; Fri, 27 Apr 2018 09:37:46 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758763AbeD0Qg2 (ORCPT + 99 others); Fri, 27 Apr 2018 12:36:28 -0400 Received: from resqmta-ch2-04v.sys.comcast.net ([69.252.207.36]:59858 "EHLO resqmta-ch2-04v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757565AbeD0Qg0 (ORCPT ); Fri, 27 Apr 2018 12:36:26 -0400 Received: from resomta-ch2-11v.sys.comcast.net ([69.252.207.107]) by resqmta-ch2-04v.sys.comcast.net with ESMTP id C2Vafl79ZrMZtC6MDfkf8m; Fri, 27 Apr 2018 16:36:25 +0000 Received: from gentwo.org ([98.222.162.64]) by resomta-ch2-11v.sys.comcast.net with ESMTPA id C6MBfr6cWQCcnC6MBfzYl5; Fri, 27 Apr 2018 16:36:25 +0000 Received: by gentwo.org (Postfix, from userid 1001) id 2D1C81161665; Fri, 27 Apr 2018 11:36:23 -0500 (CDT) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id 2A6E2116012E; Fri, 27 Apr 2018 11:36:23 -0500 (CDT) Date: Fri, 27 Apr 2018 11:36:23 -0500 (CDT) From: Christopher Lameter X-X-Sender: cl@nuc-kabylake To: Matthew Wilcox cc: Michal Hocko , Christoph Hellwig , "Luis R. Rodriguez" , linux-mm@kvack.org, Jan Kara , matthew@wil.cx, x86@kernel.org, luto@amacapital.net, martin.petersen@oracle.com, jthumshirn@suse.de, broonie@kernel.org, linux-spi@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, "lsf-pc@lists.linux-foundation.org" Subject: Re: [LSF/MM TOPIC NOTES] x86 ZONE_DMA love In-Reply-To: <20180427161813.GD8161@bombadil.infradead.org> Message-ID: References: <20180426215406.GB27853@wotan.suse.de> <20180427053556.GB11339@infradead.org> <20180427071843.GB17484@dhcp22.suse.cz> <20180427161813.GD8161@bombadil.infradead.org> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-CMAE-Envelope: MS4wfA/draW3ZiTEfMyQ4beOORMbvaLvXe09S4jHIdjBr/9t2jsdv10+XlNlQTCu+BbqUZ7ZakG8aSBsJnxATAg9+/mfx9pGecdkCw0yK6c66n1h22EE0kAP vyIpQJ6m7S0H9JWsl1zxdziJmtcqKbBZpBnKyOO5OSXTeXvUerOdNBjaJv2fobnvou4L04wONxqZDYhPM2XZYZNVfW5FjgKYihdNTqQpJT12Y7jlXyGEFjS2 Gdt4TqQY9yZM6A8ZWM/hxJCUhK5yaqxyzw551AjalOjlmD/keQD8250qlTpgS5nz4FSeA5djuRhxwNbgyXY3aC6sPMmMSNMz8/gsbTl2NdkNAdh0eNiFLx9b 6MUfLV9Xwn8xM9lLT1iVRAvZHUNoCSb9Vyl4yYG6NJYacqm24mGFIV2PQj4PnZidp7lKDnVYucZDAYVl1v3WIABv1CzmviI2K0K9SGID5aV+MZ6Rr72SRS3j D9myGQd76xn+CF/sjEwHd5iMIMUXj26nCw4Cb7P/xx4VVo8cnMt553vCtYRl/5EZKiaSDi3L5tcmZWlLSyBXpX0b2LgDWhVNK77XcN06Lqpt9Q62tEKhyTLT KjmnYSN15HhIeppWNfS1bMQ96WmunonJqauylWUc7bgRTg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Apr 2018, Matthew Wilcox wrote: > Some devices have incredibly bogus hardware like 28 bit addressing > or 39 bit addressing. We don't have a good way to allocate memory by > physical address other than than saying "GFP_DMA for anything less than > 32, GFP_DMA32 (or GFP_KERNEL on 32-bit) for anything less than 64 bit". > > Even CMA doesn't have a "cma_alloc_phys()". Maybe that's the right place > to put such an allocation API. The other way out of this would be to require a IOMMU?