From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934534AbcKJP7r (ORCPT ); Thu, 10 Nov 2016 10:59:47 -0500 Received: from 8bytes.org ([81.169.241.247]:60693 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933398AbcKJP7p (ORCPT ); Thu, 10 Nov 2016 10:59:45 -0500 Date: Thu, 10 Nov 2016 16:59:39 +0100 From: Joerg Roedel To: Robin Murphy Cc: Marek Szyprowski , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] iommu/dma-iommu: properly respect configured address space size Message-ID: <20161110155938.GI2078@8bytes.org> References: <1478523973-8828-1-git-send-email-m.szyprowski@samsung.com> <68e7a18b-739e-b73e-eacf-3cb6c1bd279a@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <68e7a18b-739e-b73e-eacf-3cb6c1bd279a@arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 08, 2016 at 11:37:23AM +0000, Robin Murphy wrote: > TBH I've been pondering ripping the size stuff out of dma-iommu, as it > all stems from me originally failing to understand what dma_32bit_pfn is > actually for. The point of dma_32bit_pfn is to allocate dma-address below 4G by default. This is a performance optimization so that even devices capable of 64bit DMA are using SAC by default instead of DAC. Since it is the goal to share a dma-iommu implemenation between architectures, I would rather prefer not to rip this stuff out. Joerg