How does Xen implement writable page table ?

Xinxin Jin
2012-10-03T20:28:27Z

Hi everyone,
If I follow the source code correctly,  fixup_page_fault() ->
ptwr_do_page_fault handles the write attempts to a page table. In my
understanding, guests update page table through two ways:
1) Issue hypercall update_va_mapping to update PDT;
2) Modify writable bottom-level ptes and then trap to Xen''s
ptwr_do_page_fualt
Here is my confusion: Why Xen supports two page table updating mechanisms?
 Why cannot apply writable page table to PDT entries?
Thanks a lot !!
--
Xinxin


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org