On Sun, 30 Mar 2008 17:55:26 +0800 "Wu Yu" <vestige.lug@xxxxxxxxx> wrote: > Hi all, > AFAIK, for IA-32 arch, two-level paging is sufficient. But the > positions of PUD and PMD are kept. This is done so all architectures can use the same iterative functions, like unmap_page_range -> zap_pud_range -> zap_pmd_range -> zap_pte_range. > I don't quite understand the word "mapping". Does that mean there > is one entry in PGD for both PUD and PMD? It means that the kernel pretends that the pgd entry points to a pud (with one entry), even though it really points to a page table. By pretenting it points to itself unmap_page_range can call the next function down, zap_pud_range. We do the same thing in zap_pud_range - it calls zap_pmd_range on the same pgd entry, except now it thinks it points to a pmd. Finally, zap_pmd_range interprets the entry and sees that it points to a page table. Zap_pmd_range invokes zap_pte_range and everything works as normal. Because, on i386, we pretend that the PUD and PMD page tables only have 1 entry, the loop does not loop, but simply invokes the next function down once. -- All rights reversed. -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
