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[213.95.11.211]) by mx.google.com with ESMTPS id c13si2066650wml.29.2019.06.14.07.50.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Jun 2019 07:50:30 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by newverein.lst.de (Postfix, from userid 2407) id 94A01227A82; Fri, 14 Jun 2019 16:50:02 +0200 (CEST) Date: Fri, 14 Jun 2019 16:50:01 +0200 From: 'Christoph Hellwig' To: David Laight Cc: 'Christoph Hellwig' , Maarten Lankhorst , Maxime Ripard , Sean Paul , David Airlie , Daniel Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Ian Abbott , H Hartley Sweeten , Intel Linux Wireless , "moderated list:ARM PORT" , "dri-devel@lists.freedesktop.org" , "intel-gfx@lists.freedesktop.org" , "linux-rdma@vger.kernel.org" , "linux-media@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-wireless@vger.kernel.org" , "linux-s390@vger.kernel.org" , "devel@driverdev.osuosl.org" , "linux-mm@kvack.org" , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 16/16] dma-mapping: use exact allocation in dma_alloc_contiguous Message-ID: <20190614145001.GB9088@lst.de> References: <20190614134726.3827-1-hch@lst.de> <20190614134726.3827-17-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jun 14, 2019 at 02:15:44PM +0000, David Laight wrote: > Does this still guarantee that requests for 16k will not cross a 16k boundary? > It looks like you are losing the alignment parameter. The DMA API never gave you alignment guarantees to start with, and you can get not naturally aligned memory from many of our current implementations.