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

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Date:	Wed, 16 Jan 2008 15:54:27 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <ak@...e.de>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Glauber de Oliveira Costa <glommer@...il.com>,
	Jan Beulich <jbeulich@...ell.com>
Subject: Re: [PATCH 0 of 4] x86: some more patches


* Andi Kleen <ak@...e.de> wrote:

> >  #define PHYSICAL_PAGE_MASK	(PAGE_MASK & __PHYSICAL_MASK)
> 
> 
> I haven't tested yet, but we looked at that one earlier and I thought 
> it was ok because
> 
> #define __PHYSICAL_MASK          _AT(phys_addr_t, (_AC(1,ULL) << __PHYSICAL_MASK_SHIFT) - 1)
> 
> and 
> 
> typedef u64     phys_addr_t;
> 
> for PAE. So the expression above should have been already 64bit.

no. The problem is that PAGE_MASK is:

  #define PAGE_MASK        (~(PAGE_SIZE-1))

  #define PAGE_SIZE        (_AC(1,UL) << PAGE_SHIFT)

that's u32 on PAE, and __PHYSICAL_MASK is u64. So PAGE_MASK gets 
zero-extended to u64. So the combined mask:

  #define PHYSICAL_PAGE_MASK      (PAGE_MASK & __PHYSICAL_MASK)

has the high bits chopped off. Please try my patch.

(PHYSICAL_PAGE_MASK is broken too in the same way, i just fixed that in 
my tree - but it's not used by anything on 32-bit PAE but by PAGE_MASK)

> So I would be surprised if the patch works.

try it ...

	Ingo
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