i386: remove bogus mtrr range check

Commit 9215da33209b861b01c51382254b178a3fe92a30 "fixed" the MTRR range
check to not allow any MTRR's under the 1MB mark (since that's where the
fixed MTRR's are active).

However, that was totally bogus, since it's normal (and almost required)
to have a large variable MTRR that starts at 0, and covers some large
percentage of the whole RAM, and then using the fixed MTRR's to override
that large MTRR to handle the special ISA hole in the 640k-1M region.

The old check was bogus too (checking that no variable MTRR is used that
is entirely under the 1MB range), but at least it wasn't actively
detrimental, because no sane situation would ever trigger such MTRR
usage in the first place.

That said, the whole notion of not allowing variable MTRR's in the low
1MB is just stupid, so rather than revert the commit, this just removes
the whole sad and unnecessary check entirely.

Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Luca Palermo <darkmage@sabayonlinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 5 deletions

diff --git a/arch/i386/kernel/cpu/mtrr/generic.c b/arch/i386/kernel/cpu/mtrr/generic.c
index 6d5937891b46..5a551fb7ea7b 100644
--- a/arch/i386/kernel/cpu/mtrr/generic.c
+++ b/arch/i386/kernel/cpu/mtrr/generic.c
@@ -469,11 +469,6 @@ int generic_validate_add_page(unsigned long base, unsigned long size, unsigned i
                 }
         }
 
-        if (base < 0x100) {
-                printk(KERN_WARNING "mtrr: cannot set region below 1 MiB (0x%lx000,0x%lx000)\n",
-                       base, size);
-                return -EINVAL;
-        }
         /*  Check upper bits of base and last are equal and lower bits are 0
             for base and 1 for last  */
         last = base + size - 1;