From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:54153 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756571Ab0GNWHB (ORCPT ); Wed, 14 Jul 2010 18:07:01 -0400 Date: Wed, 14 Jul 2010 23:05:36 +0100 From: Russell King - ARM Linux Subject: Re: [RFC 1/3 v3] mm: iommu: An API to unify IOMMU, CPU and device memory management Message-ID: <20100714220536.GE18138@n2100.arm.linux.org.uk> References: <4C3C0032.5020702@codeaurora.org> <20100713150311B.fujita.tomonori@lab.ntt.co.jp> <20100713121420.GB4263@codeaurora.org> <20100714104353B.fujita.tomonori@lab.ntt.co.jp> <20100714201149.GA14008@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100714201149.GA14008@codeaurora.org> Sender: linux-arm-msm-owner@vger.kernel.org List-ID: To: Zach Pfeffer Cc: FUJITA Tomonori , ebiederm@xmission.com, linux-arch@vger.kernel.org, dwalker@codeaurora.org, mel@csn.ul.ie, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, andi@firstfloor.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org On Wed, Jul 14, 2010 at 01:11:49PM -0700, Zach Pfeffer wrote: > If the DMA-API contained functions to allocate virtual space separate > from physical space and reworked how chained buffers functioned it > would probably work - but then things start to look like the VCM API > which does graph based map management. Every additional virtual mapping of a physical buffer results in additional cache aliases on aliasing caches, and more workload for developers to sort out the cache aliasing issues. What does VCM to do mitigate that?