double kernel page table entry for the same physical page?!

[ming lei]

1. In PPC MMU_init sets up kernel page table for all
the physical pages available(say size is A) to the
virt address starting from PAGE_OFFSET to
(PAGE_OFFSET+A).

Question: does the linux ever touch this section of
page table(virt address from PAGE_OFFSET to
PAGE_OFFSET+A) again? like remove or modify one of the
entry?

2. In VMALLOC, say we have virt address
B(B>PAGE_OFFSET+A), sets up the page table entry for
this B to any one of the physical pages.

Question: For every physical page, it should already
be mapped in #1, but vmalloc maps it again to a virt
address higher. Does it mean in kernel page table, we
may have two PTE entries pointing to the same physical
page, even their virt addresses are different?

Last question:
If this is true, is this platform implemention
specific? Does i386 implemention have same situation?

Thanks,
Ming



		
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