(2010/06/17 15:03), H. Peter Anvin wrote:
On 06/16/2010 09:55 PM, Kenji Kaneshige wrote:
I think they might be. Kenji?
No. My addresses are in the 44-bits range (around fc000000000). So it is
not required for my problem. This change assumes that phys_addr can be
above 44-bits (up to 52-bits (and higher in the future?)).
By the way, is there linux kernel limit regarding above 44-bits physical
address in x86_32 PAE? For example, pfn above 32-bits is not supported?
There are probably places at which PFNs are held in 32-bit numbers,
although it would be good to track them down if it isn't too expensive
to fix them (i.e. doesn't affect generic code.)
This also affects paravirt systems, i.e. right now Xen has to locate all
32-bit guests below 64 GB, which limits its usefulness.
#ifdef CONFIG_X86_PAE
/* 44=32+12, the limit we can fit into an unsigned long pfn */
#define __PHYSICAL_MASK_SHIFT 44
#define __VIRTUAL_MASK_SHIFT 32
If there is 44-bits physical address limit, I think it's better to use
PHYSICAL_PAGE_MASK for masking physical address, instead of "(phys_addr
PAGE_SHIFT)<< PAGE_SHIFT)". The PHYSICAL_PAGE_MASK would become
greater value when 44-bits physical address limit is eliminated. And
maybe we need to change phys_addr_valid() returns error if physical
address is above (1<< __PHYSICAL_MASK_SHIFT)?
The real question is how much we can fix without an unreasonable cost.
Thank you very much. I understand the situation.
Thanks,
Kenji Kaneshige
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