linux-kernel - Re: [PATCH 0 of 4] x86: some more patches

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Date:	Wed, 16 Jan 2008 16:47:10 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jan Beulich <jbeulich@...ell.com>
Cc:	Andi Kleen <ak@...e.de>,
	Glauber de Oliveira Costa <glommer@...il.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0 of 4] x86: some more patches


* Jan Beulich <jbeulich@...ell.com> wrote:

> > Yes, but if you cast to long the result will be 32bit again. Or do 
> > you rely on it being always used in 64bit signed context with sign 
> > extension? While that might work it would seem rather fragile to me, 
> > just asking for similar future bugs.
> 
> Even if conversion is to 64-bit unsigned, the value (being signed) 
> will be sign-extended first (to preserve its value modulo 2**<target 
> type width>).

yes. It would be nice if Andi could test my fix instead of arguing why 
he thinks it's unlikely to work ;-)

(i've got the cleanup patch below as well ontop of today's x86.git which 
includes the first fix, but it's an RFC as it has wider impact and might 
break stuff.)

	Ingo

--------------->
Subject: x86: PAGE_MASK cleanup
From: Ingo Molnar <mingo@...e.hu>

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 include/asm-x86/page.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-x86.q/include/asm-x86/page.h
===================================================================
--- linux-x86.q.orig/include/asm-x86/page.h
+++ linux-x86.q/include/asm-x86/page.h
@@ -6,12 +6,12 @@
 /* PAGE_SHIFT determines the page size */
 #define PAGE_SHIFT	12
 #define PAGE_SIZE	(_AC(1,UL) << PAGE_SHIFT)
-#define PAGE_MASK	(~(PAGE_SIZE-1))
+#define PAGE_MASK	(_AT(phys_addr_t, ~(PAGE_SIZE-1)))
 
 #ifdef __KERNEL__
 
 #define PHYSICAL_PAGE_MASK	(PAGE_MASK & __PHYSICAL_MASK)
-#define PTE_MASK		(_AT(long, PHYSICAL_PAGE_MASK))
+#define PTE_MASK		PHYSICAL_PAGE_MASK
 
 #define LARGE_PAGE_SIZE		(_AC(1,UL) << PMD_SHIFT)
 #define LARGE_PAGE_MASK		(~(LARGE_PAGE_SIZE-1))
--
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