>>> Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> 18.02.09 04:39 >>>
First a general remark: You're doing this patch to support 256G domains,
but by keeping extend_init_mapping() there'll continue to be no way to
support domains with close to or above 512G (or, if making use of
XEN_ELFNOTE_INIT_P2M, 1T). This function, rather than needing fixes,
really just needs to go away.
I've done this in our forward ported 2.6.27+ kernels, but unfortunately
can't really contribute the changes to the 2.6.18 tree, as there are too
many differences, and I'm simply lacking the time (and, honestly, interest)
to work out all the issues. I could post the respective patch if you (or
someone else) care(s).
>--- init-xen.c.orig 2009-02-17 18:58:58.716954000 -0800
>+++ init-xen.c 2009-02-17 19:33:57.310074000 -0800
>@@ -587,35 +587,45 @@ void __init xen_init_pt(void)
> static void __init extend_init_mapping(unsigned long tables_space)
> {
> unsigned long va = __START_KERNEL_map;
>- unsigned long phys, addr, *pte_page;
>+ unsigned long phys, addr, *pte_page, *pmd_page;
>+ pud_t *pud;
> pmd_t *pmd;
> pte_t *pte, new_pte;
>- unsigned long *page = (unsigned long *)init_level4_pgt;
>+ unsigned long *pud_page = (unsigned long *)init_level4_pgt;
This is certainly confusing. Please use typeless names here, or names
that properly reflect what they're used for.
>
>- addr = page[pgd_index(va)];
>- addr_to_page(addr, page);
>- addr = page[pud_index(va)];
>- addr_to_page(addr, page);
>-
>- /* Kill mapping of low 1MB. */
>+ /* Kill low mappings */
> while (va < (unsigned long)&_text) {
> if (HYPERVISOR_update_va_mapping(va, __pte_ma(0), 0))
> BUG();
> va += PAGE_SIZE;
> }
>+ addr = pud_page[pgd_index(va)]; /* get pud entry from pgd tbl */
>+ addr_to_page(addr, pud_page); /* pud_page now va of pud tbl */
If you follow above request for using proper (or type-neutral) names, you
won't need extra comments here.
Also, the code could stay at the place it was so far (since clearly pgd_index()
can never be different for __START_KERNEL_map and _text).
>
> /* Ensure init mappings cover kernel text/data and initial tables. */
> while (va < (__START_KERNEL_map
> + (start_pfn << PAGE_SHIFT)
> + tables_space)) {
>- pmd = (pmd_t *)&page[pmd_index(va)];
>+
>+ pud = (pud_t *)&pud_page[pud_index(va)]; /* get pud entry
>*/
>+ if (pud_none(*pud)) {
>+ pmd_page = alloc_static_page(&phys);
>+ early_make_page_readonly(
>+ pmd_page, XENFEAT_writable_page_tables);
>+ set_pud(pud, __pud(phys | _KERNPG_TABLE));
>+ } else {
>+ addr = pud_page[pud_index(va)];
>+ addr_to_page(addr, pmd_page);
>+ }
>+
>+ pmd = (pmd_t *)&pmd_page[pmd_index(va)];
> if (pmd_none(*pmd)) {
> pte_page = alloc_static_page(&phys);
> early_make_page_readonly(
> pte_page, XENFEAT_writable_page_tables);
> set_pmd(pmd, __pmd(phys | _KERNPG_TABLE));
> } else {
>- addr = page[pmd_index(va)];
>+ addr = pmd_page[pmd_index(va)];
> addr_to_page(addr, pte_page);
> }
> pte = (pte_t *)&pte_page[pte_index(va)];
>@@ -630,7 +640,7 @@ static void __init extend_init_mapping(u
>
> /* Finally, blow away any spurious initial mappings. */
> while (1) {
Didn't you indicate in an earlier mail that we're lacking a pud_none() check
here? Just by adding the pud allocation above, you're not excluding to
run over a pud entry boundary here.
Likewise would pmd_page need to be updated here when you cross a
pud entry boundary.
>- pmd = (pmd_t *)&page[pmd_index(va)];
>+ pmd = (pmd_t *)&pmd_page[pmd_index(va)];
> if (pmd_none(*pmd))
> break;
> if (HYPERVISOR_update_va_mapping(va, __pte_ma(0), 0))
>@@ -719,6 +729,7 @@ static void xen_finish_init_mapping(void
> table_end = start_pfn;
> }
>
>+
> /* Setup the direct mapping of the physical memory at PAGE_OFFSET.
> This runs before bootmem is initialized and gets pages directly from the
> physical memory. To access them they are temporarily mapped. */
Please omit this last hunk altogether.
Jan
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