[PATCH] x86: fix alignment determination in range_to_mtrr()

[PATCH] x86: fix alignment determination in range_to_mtrr()

[Jan Beulich]

With the variable operated on being of "unsigned long" type, neither
ffs() nor fls() are suitable to use on them, as those truncate their
arguments to 32 bits. Using __ffs() and __fls() respectively at once
eliminates the need t subtract 1 from their results.

Additionally, with the alignment value subsequently used as a shift
count, it must be enforced to be less than BITS_PER_LONG (and on 64-bit
there's no need for it to be any smaller).

Signed-off-by: Jan Beulich <jbeulich@suse.com>

---
 arch/x86/kernel/cpu/mtrr/cleanup.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- 3.5-rc5/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ 3.5-rc5-x86-mtrr-cleanup-types/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -258,11 +258,11 @@ range_to_mtrr(unsigned int reg, unsigned
 
 		/* Compute the maximum size with which we can make a range: */
 		if (range_startk)
-			max_align = ffs(range_startk) - 1;
+			max_align = __ffs(range_startk);
 		else
-			max_align = 32;
+			max_align = BITS_PER_LONG - 1;
 
-		align = fls(range_sizek) - 1;
+		align = __fls(range_sizek);
 		if (align > max_align)
 			align = max_align;
 

[tip:x86/asm] x86/mm/mtrr: Fix alignment determination in range_to_mtrr()

[tip-bot for Jan Beulich]

Commit-ID:  1ba9a294141b106b7247649a5c3372d8284eca80
Gitweb:     http://git.kernel.org/tip/1ba9a294141b106b7247649a5c3372d8284eca80
Author:     Jan Beulich <JBeulich@suse.com>
AuthorDate: Fri, 6 Jul 2012 15:07:48 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 10 Jul 2012 10:38:14 +0200

x86/mm/mtrr: Fix alignment determination in range_to_mtrr()

With the variable operated on being of "unsigned long" type,
neither ffs() nor fls() are suitable to use on them, as those
truncate their arguments to 32 bits. Using __ffs() and __fls()
respectively at once eliminates the need to subtract 1 from their
results.

Additionally, with the alignment value subsequently used as a
shift count, it must be enforced to be less than BITS_PER_LONG
(and on 64-bit there's no need for it to be any smaller).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/4FF70D54020000780008E179@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/mtrr/cleanup.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
index bdda2e6..35ffda5 100644
--- a/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -258,11 +258,11 @@ range_to_mtrr(unsigned int reg, unsigned long range_startk,
 
 		/* Compute the maximum size with which we can make a range: */
 		if (range_startk)
-			max_align = ffs(range_startk) - 1;
+			max_align = __ffs(range_startk);
 		else
-			max_align = 32;
+			max_align = BITS_PER_LONG - 1;
 
-		align = fls(range_sizek) - 1;
+		align = __fls(range_sizek);
 		if (align > max_align)
 			align = max_align;