From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH 0/5] Implement SMMU passthrough using the default domain Date: Thu, 26 Jan 2017 18:18:58 +0100 Message-ID: <20170126171857.GE27598@8bytes.org> References: <1484849955-1871-1-git-send-email-will.deacon@arm.com> <010801d27654$47b7e450$d727acf0$@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <010801d27654$47b7e450$d727acf0$@codeaurora.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Sricharan Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, 'Will Deacon' , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: iommu@lists.linux-foundation.org On Tue, Jan 24, 2017 at 08:42:23PM +0530, Sricharan wrote: > Thanks for this series. We had a case with the GPU. > The GPU's iommu was setup by kernel and the GPU > also does dynamic updates for on-the-fly switching between > process pagetables. GPU driver was not using DMA domain and > the GPU's firmware was always expecting to run out of contextbank > '0' (although not correct) , which was not the case after the DMA domain > was made default as '0' was getting allocated for DMA domain and > there were concerns about reusing the DMA domain as well. > Now with this series, looks there is an way out of that that can be tried. > > So should the default domain not be per device specific selectable ? Note that iommu-drivers can request direct-mapping for any given device on its initializtion. This is used on x86 for devices that need a 1-1 mapping for some reason. Also device drivers can use the iommu-api and assign their own domain to a device, which allows them to manage the dma address space on their own. Joerg