x86: mtrr: Fix high_width computation when phys-addr is >= 44bit

found one system where cpu address line is 44bits, mtrr printout
is not right:

 [    0.000000] MTRR variable ranges enabled:
 [    0.000000]   0 base 0   00000000 mask FF0 00000000 write-back
 [    0.000000]   1 base 10  00000000 mask FFF 80000000 write-back
 [    0.000000]   2 base 0   80000000 mask FFF 80000000 uncachable
 [    0.000000]   3 base 0   7F800000 mask FFF FF800000 uncachable

Li Zefan and Frederic pointed out the high_width could be -4 some how.

It turns out when phys_addr is 44bit, size_or_mask will be
ffffffff,00000000 so ffs(size_or_mask) will be 0.

Try to check low 32 bit, to get correct high_width.

Signed-off-by: Yinghai Lu <yinghai@kerne.org>
Also-analyzed-by: Frederic Weisbecker <fweisbec@gmail.com>
Also-analyzed-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4A026540.8060504@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 0b776c09aff3..d21d4fb161f7 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -275,7 +275,11 @@ static void __init print_mtrr_state(void)
         }
         printk(KERN_DEBUG "MTRR variable ranges %sabled:\n",
                mtrr_state.enabled & 2 ? "en" : "dis");
-        high_width = ((size_or_mask ? ffs(size_or_mask) - 1 : 32) - (32 - PAGE_SHIFT) + 3) / 4;
+        if (size_or_mask & 0xffffffffUL)
+                high_width = ffs(size_or_mask & 0xffffffffUL) - 1;
+        else
+                high_width = ffs(size_or_mask>>32) + 32 - 1;
+        high_width = (high_width - (32 - PAGE_SHIFT) + 3) / 4;
         for (i = 0; i < num_var_ranges; ++i) {
                 if (mtrr_state.var_ranges[i].mask_lo & (1 << 11))
                         printk(KERN_DEBUG "  %u base %0*X%05X000 mask %0*X%05X000 %s\n",