diff options
author | Jeremy Fitzhardinge <jeremy@goop.org> | 2008-06-06 10:21:39 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-06-19 10:08:44 +0200 |
commit | ad524d46f36bbc32033bb72ba42958f12bf49b06 (patch) | |
tree | 6147475fc20e81345dcf04486d8ea422df141951 /arch/x86/Kconfig.cpu | |
parent | 9bedbcb207ed9a571b239231d99c8fd4a34ae24d (diff) |
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>
Diffstat (limited to 'arch/x86/Kconfig.cpu')
0 files changed, 0 insertions, 0 deletions