x86: PAT infrastructure patch

Sets up pat_init() infrastructure.

PAT MSR has following setting.
	PAT
	|PCD
	||PWT
	|||
	000 WB		_PAGE_CACHE_WB
	001 WC		_PAGE_CACHE_WC
	010 UC-		_PAGE_CACHE_UC_MINUS
	011 UC		_PAGE_CACHE_UC

We are effectively changing WT from boot time setting to WC.
UC_MINUS is used to provide backward compatibility to existing /dev/mem
users(X).

reserve_memtype and free_memtype are new interfaces for maintaining alias-free
mapping. It is currently implemented in a simple way with a linked list and
not optimized. reserve and free tracks the effective memory type, as a result
of PAT and MTRR setting rather than what is actually requested in PAT.

pat_init piggy backs on mtrr_init as the rules for setting both pat and mtrr
are same.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index fd27048087b8..5b46756e4c7c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1009,6 +1009,21 @@ config MTRR
 
           See <file:Documentation/mtrr.txt> for more information.
 
+config X86_PAT
+        def_bool y
+        prompt "x86 PAT support"
+        depends on MTRR && NONPROMISC_DEVMEM
+        help
+          Use PAT attributes to setup page level cache control.
+        ---help---
+          PATs are the modern equivalents of MTRRs and are much more
+          flexible than MTRRs.
+
+          Say N here if you see bootup problems (boot crash, boot hang,
+          spontaneous reboots) or a non-working Xorg.
+
+          If unsure, say Y.
+
 config EFI
         def_bool n
         prompt "EFI runtime service support"