tree 212ee811a6271eb77e887d4f63817c01606ae8a2
parent e1b4d1143651fb3838be1117785b6e0386fa151f
author Eric Anholt <eric@anholt.net> 1232748861 -0800
committer Ingo Molnar <mingo@elte.hu> 1232964867 +0100

x86: work around PAGE_KERNEL_WC not getting WC in iomap_atomic_prot_pfn.

In the absence of PAT, PAGE_KERNEL_WC ends up mapping to a memory type that
gets UC behavior even in the presence of a WC MTRR covering the area in
question.  By swapping to PAGE_KERNEL_UC_MINUS, we can get the actual
behavior the caller wanted (WC if you can manage it, UC otherwise).

This recovers the 40% performance improvement of using WC in the DRM
to upload vertex data.

Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>