[PATCH] i386: fix buggy MTRR address checks

Fix checks that failed to realize that values are 4-kB-unit-sized (note the
format strings in this same diff context which *do* realize the unit size,
via appended "000"!).  Also fix an incorrect below-1MB area check (as
gathered from Jan Beulich's unapplied patch at
http://www.ussg.iu.edu/hypermail/linux/kernel/0411.1/1378.html ) Update
mtrr_add_page() docu to make 4-kB-sized calculation more obvious.

Given several further items mentioned in Jan's patch mail, all in all MTRR
code seems surprisingly buggy, for a surprisingly long period of time (many
years).  Further work/investigation would be useful.

TBD Note that my patch is pretty much UNTESTED, since I can only verify that it
TBD successfully boots my machine, but I cannot test against actual buggy
TBD hardware which would require these (formerly broken) checks.  Long -mm
TBD simmering would make sense, especially since these now-working checks might
TBD turn out to have adverse effects on unaffected hardware.

Signed-off-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Andi Kleen <ak@suse.de>
Acked-by: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/i386/kernel/cpu/mtrr/main.c b/arch/i386/kernel/cpu/mtrr/main.c
index fff90bda4733..2b8b0b361ccb 100644
--- a/arch/i386/kernel/cpu/mtrr/main.c
+++ b/arch/i386/kernel/cpu/mtrr/main.c
@@ -263,8 +263,8 @@ static void set_mtrr(unsigned int reg, unsigned long base,
 
 /**
  *      mtrr_add_page - Add a memory type region
- *      @base: Physical base address of region in pages (4 KB)
- *      @size: Physical size of region in pages (4 KB)
+ *      @base: Physical base address of region in pages (in units of 4 kB!)
+ *      @size: Physical size of region in pages (4 kB)
  *      @type: Type of MTRR desired
  *      @increment: If this is true do usage counting on the region
  *