On Thu, Feb 2, 2017 at 10:12 AM, Will Deacon <will.dea...@arm.com> wrote: > 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. >
Only relation is if we were trying to solve the case of a driver that needs to manage it's own domain with this patchset.. but that seems a bit like "when all you have is a hammer, everything looks like a nail".. BR, -R _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu