linux-kernel - Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue

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Date:	Wed, 27 Jul 2011 19:10:15 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Borislav Petkov <bp@...64.org>, "H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"Przywara, Andre" <Andre.Przywara@....com>,
	"Pohlack, Martin" <Martin.Pohlack@....com>
Subject: Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue

On Sun, Jul 24, 2011 at 01:39:25PM -0400, Linus Torvalds wrote:
> > Yeah, I like the BITS() thing - will change. I actually have a similar
> > macro GENMASK(o, hi) in <drivers/edac/amd64_edac.h> - I should move it
> > to <linux/bitops.h> and rename it to BITS().
> 
> So it may be that BITS() is much too generic a name, and will cause
> problems. A quick "git grep -w BITS" certainly finds a fair number of
> hits. So I don't think it's usable as-is, it was meant more as
> pseudo-code.

How about something like the following instead - it should take care
of all your bitmask generating needs. There are also a couple of
GENMASK/BITMASK identical definitions around the tree which can be
unified while I'm at it too.

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index a3ef66a..b1970e3 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -6,6 +6,19 @@
 #define BIT(nr)                        (1UL << (nr))
 #define BIT_MASK(nr)           (1UL << ((nr) % BITS_PER_LONG))
 #define BIT_WORD(nr)           ((nr) / BITS_PER_LONG)
+
+/*
+ * Create a contiguous bitmask starting at bit position @lo and ending at
+ * position @hi. For example
+ *
+ * GENMASK_ULL(21, 39) gives us the 64bit vector 0x000000ffffe00000.
+ */
+#define _GENMASK_T(cast, type, lo, hi) \
+       (((cast)(1##type << ((hi) - (lo) + 1)) - 1) << (lo))
+#define GENMASK(lo, hi)                _GENMASK_T(unsigned, U, lo, hi)
+#define GENMASK_UL(lo, hi)     _GENMASK_T(unsigned long, UL, lo, hi)
+#define GENMASK_ULL(lo, hi)    _GENMASK_T(unsigned long long, ULL, lo, hi)
+
 #define BITS_PER_BYTE          8
 #define BITS_TO_LONGS(nr)      DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
 #endif

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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