linux-kernel - [PATCH] x86: fix alignment determination in range_to

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Message-Id: <4FF70D54020000780008E179@nat28.tlf.novell.com>
Date:	Fri, 06 Jul 2012 15:07:48 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: [PATCH] x86: 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 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@...e.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;
 



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