On Thu, Feb 02, 2017 at 10:02:50AM -0500, Rob Clark wrote: > On Thu, Jan 26, 2017 at 12:18 PM, Joerg Roedel <j...@8bytes.org> wrote: > > 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. > > Part of the problem is that dev->archdata.dma_ops gets wired up to > iommu_dma_ops. Which isn't so bad on it's own, except that cache ops > are not exposed to drivers, forcing us to use dma-mapping API > (dma_map_sg, etc) for cache operations. > > Possibly we should just expose cache op's to drivers bypass this abuse > of dma-mapping. > > btw, Will, we definitely want this to *not* rely on kcmdline for the > gpu with it's own private iommu case..
I still need to understand the unmanaged domain case, but I don't really see why that's related to this series to be honest. Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
