Messages in this thread Patch in this message | | | Date | Fri, 06 Jun 2008 10:21:39 +0100 | From | Jeremy Fitzhardinge <> | Subject | [PATCH UPDATED] x86: set PAE PHYSICAL_MASK_SHIFT to 44 bits. |
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When a 64-bit x86 processor runs in 32-bit PAE mode, a pte can potentially have the same number of physical address bits as the 64-bit host ("Enhanced Legacy PAE Paging"). This means, in theory, we could have up to 52 bits of physical address in a pte.
The 32-bit kernel uses a 32-bit unsigned long to represent a pfn. This means that it can only represent physical addresses up to 32+12=44 bits wide. Rather than widening pfns everywhere, just set 2^44 as the Linux x86_32-PAE architectural limit for physical address size.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Jan Beulich <jbeulich@novell.com> --- include/asm-x86/page_32.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
=================================================================== --- a/include/asm-x86/page_32.h +++ b/include/asm-x86/page_32.h @@ -22,7 +22,8 @@ #ifdef CONFIG_X86_PAE -#define __PHYSICAL_MASK_SHIFT 36 +/* 44=32+12, the limit we can fit into an unsigned long pfn */ +#define __PHYSICAL_MASK_SHIFT 44 #define __VIRTUAL_MASK_SHIFT 32 #define PAGETABLE_LEVELS 3
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