Re: [PATCH UPDATED] x86: set PAE PHYSICAL_MASK_SHIFT to 44 bits.

Jeremy Fitzhardinge
2008-06-10T13:07:29Z

Ingo Molnar wrote:
>> 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.
>>
>
> applied to tip/x86/cleanups - thanks Jeremy. No urgency for v2.6.26,
> right?

Not urgent, but it would be nice to have.

J