From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [PATCH 2/6] PCI DMA API Date: Sun, 30 Mar 2008 09:56:04 -0500 Message-ID: <47EFAA04.50903@us.ibm.com> References: <1206827760-4566-1-git-send-email-aliguori@us.ibm.com> <1206827760-4566-2-git-send-email-aliguori@us.ibm.com> <47EFA769.7090201@us.ibm.com> <47EFA86F.8020905@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Blue Swirl , kvm-devel@lists.sourceforge.net, Marcelo Tosatti , qemu-devel@nongnu.org, Aurelien Jarno To: Avi Kivity Return-path: In-Reply-To: <47EFA86F.8020905@qumranet.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Avi Kivity wrote: > Anthony Liguori wrote: > >>> This looks like it wouldn't scale to handle the Sparc systems. There >>> we want to make more translation steps from DVMA addresses to physical >>> in DMA controller and IOMMU and only in the final stage to void *. To >>> handle this, probably there should be an opaque parameter and some way >>> to register the translation function. Otherwise the API looks OK. >>> >>> >> I think having the PCI DMA API translate PhysIOVector => PhysIOVector >> would help. Then it becomes pretty easy to just call the DMA >> controller for additional translation from the IOMMU. >> >> Does that sound right? I don't quite understand what role the opaque >> parameter would serve. >> >> > > State for the dma controller. > > I think Blue is calling for chaining of dma mappings, no? Something > similar is being proposed for the Linux dma api. > > The way I envision chaining is: virtio-blk calls pci_device_dma_map with a PhysIOVector A pci_device_dma_map calls into PCI IOMMU (if necessary) to translate PhysIOVector A to PhysIOVector B pci_device_dma_map then calls into platform DMA engine to translate PhysIOVector B to PhysIOVector C pci_device_dma_map frees PhysIOVector B and returns PhysIOVector C Regards, Anthony Liguori ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace