[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] pagetable RO
>>> On 11.10.13 at 19:27, åæ<zhangzhi2022@xxxxxxxxxxx> wrote: > I've read the source code of do_mmu_update and could only find that macro: > define_get_linear_pagetable(l2) checks whether its entry is read-only. > However, this function does execute only when > get_page_and_type_from_pagenr(mfn, PGT_l1_page_table, ...) returns an invalid > value. Is this the point or somewhere else about checking whether the new > PGT_l1_page_table as read-only ? I did not find the check points in the > function: get_page_and_type_from_pagenr(mfn, PGT_l1_page_table, ...) as well > as its sub-branch functions. That's not how it works. A page is read-only if it's of one of the types that require it to be and has non-zero type reference count, or if it's of no particular type (i.e. its type reference count is zero). Any mapping with _PAGE_RW set would cause the page to have a non- zero type reference count and be of type PGT_writable, and hence it couldn't be transitioned to any of the other (read-only) types. The core function here is __get_page_type(). Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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