From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:33542) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S1laW-0008BS-I3 for qemu-devel@nongnu.org; Sun, 26 Feb 2012 16:25:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S1laV-0003zo-3W for qemu-devel@nongnu.org; Sun, 26 Feb 2012 16:25:00 -0500 Received: from mail-ey0-f173.google.com ([209.85.215.173]:58090) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S1laU-0003zk-St for qemu-devel@nongnu.org; Sun, 26 Feb 2012 16:24:59 -0500 Received: by eaan13 with SMTP id n13so1490931eaa.4 for ; Sun, 26 Feb 2012 13:24:57 -0800 (PST) Sender: Eduard - Gabriel Munteanu Date: Sun, 26 Feb 2012 23:24:11 +0200 From: Eduard - Gabriel Munteanu Message-ID: <20120226212411.GB3671@localhost> References: <1330054063-16860-1-git-send-email-david@gibson.dropbear.id.au> <1330054063-16860-5-git-send-email-david@gibson.dropbear.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1330054063-16860-5-git-send-email-david@gibson.dropbear.id.au> Subject: Re: [Qemu-devel] [PATCH 4/8] Add universal DMA helper functions List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: Joerg Rodel , Richard Henderson , qemu-devel@nongnu.org, anthony@codemonkey.ws, "Michael S. Tsirkin" On Fri, Feb 24, 2012 at 02:27:39PM +1100, David Gibson wrote: > Not that long ago, every device implementation using DMA directly > accessed guest memory using cpu_physical_memory_*(). This meant that > adding support for a guest visible IOMMU would require changing every > one of these devices to go through IOMMU translation. > > Shortly before qemu 1.0, I made a start on fixing this by providing > helper functions for PCI DMA. These are currently just stubs which > call the direct access functions, but mean that an IOMMU can be > implemented in one place, rather than for every PCI device. > > Clearly, this doesn't help for non PCI devices, which could also be > IOMMU translated on some platforms. It is also problematic for the > devices which have both PCI and non-PCI version (e.g. OHCI, AHCI) - we > cannot use the the pci_dma_*() functions, because they assume the > presence of a PCIDevice, but we don't want to have to check between > pci_dma_*() and cpu_physical_memory_*() every time we do a DMA in the > device code. > > This patch makes the first step on addressing both these problems, by > introducing new (stub) dma helper functions which can be used for any > DMA capable device. > > These dma functions take a DMAContext *, a new (currently empty) > variable describing the DMA address space in which the operation is to > take place. NULL indicates untranslated DMA directly into guest > physical address space. The intention is that in future non-NULL > values will given information about any necessary IOMMU translation. > > DMA using devices must obtain a DMAContext (or, potentially, contexts) > from their bus or platform. For now this patch just converts the PCI > wrappers to be implemented in terms of the universal wrappers, > converting other drivers can take place over time. > > Cc: Michael S. Tsirkin > Cc: Joerg Rodel > Cc: Eduard - Gabriel Munteanu > Cc: Richard Henderson > > Signed-off-by: David Gibson Hi, Thanks for pushing this forward. I got caught up in other stuff, perhaps I'll be able to beat you to submitting the actual implementation soon. :-) [snip] Eduard