x86: set PAE PHYSICAL_MASK_SHIFT to 44 bits.
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. This is a bugfix for two cases: 1. running a 32-bit PAE kernel on a machine with more than 64GB RAM. 2. running a 32-bit PAE Xen guest on a host machine with more than 64GB RAM In both cases, a pte could need to have more than 36 bits of physical, and masking it to 36-bits will cause fairly severe havoc. Signed-off-by:Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Jan Beulich <jbeulich@novell.com> Cc: <stable@kernel.org> Signed-off-by:
Ingo Molnar <mingo@elte.hu>
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