"GPU device drivers are increasingly requiring more sophisticated
support for mapping objects into both userland and the kernel. For
example, memory used for textures often needs to be mapped
Write-Combining rather than Write-Back. I have recently created three
patches to provide several extensions.
"The first patch allows device drivers to use a different VM object to
back specific mmap() calls instead of always using the device pager.
The second patch introduces a new VM object type that can map an
arbitrary set of physical address ranges. This can be used to let
userland mmap PCI BARs, etc. The third patch allows memory mappings to
use different caching modes (e.g. Write-Combining or Uncacheable).
"Together I believe these patches provide the remaining pieces needed
for an Nvidia amd64 driver. They will also be useful for future Xorg
DRM support as well. The current set of patches can be safely merged
back to 7.x as well."
