Inability of Linux Kernel to support 1GB physical memory and the HIGHMEM solution -


i have been reading [1] have idea highmem. article says "if kernel wishes able access system's physical memory directly, however, must set page tables map memory kernel's part of address space" .that have confusion. mean accessing physical memory directly? mean explicitly stating physical address?(afaik, not possible in linux kernel) go on stating "it must set page tables map memory kernel's part of address space". in highmem solution,isn't it? please me understand problem lead highmem solution.

[1] http://lwn.net/articles/75174/

1 if kernel wishes able access system's physical memory directly, however, must set page tables map memory kernel's part of address space
i think author want emphasize kernel need page table address physical memory.

2 t must set page tables map memory kernel's part of address space kernel part of address space need page tables map memory, while high memory, instead, has no direct kernel mapping. can find sentences on article "when kernel needs work page in high memory, must explicitly set special page table map kernel's address space first."


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