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SubjectRe: [PATCH 26/46] x86, mm, Xen: Remove mapping_pagetable_reserve()
On Mon, 12 Nov 2012, Yinghai Lu wrote:
> Page table area are pre-mapped now after
> x86, mm: setup page table in top-down
> x86, mm: Remove early_memremap workaround for page table accessing on 64bit
>
> mapping_pagetable_reserve is not used anymore, so remove it.

You should mention in the description of the patch that you are
removing mask_rw_pte too.

The reason why you can do that safely is that you previously modified
allow_low_page to always return pages that are already mapped, moreover
xen_alloc_pte_init, xen_alloc_pmd_init, etc, will mark the page RO
before hooking it into the pagetable automatically.

[ ... ]

> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index dcf5f2d..bbb883f 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1178,20 +1178,6 @@ static void xen_exit_mmap(struct mm_struct *mm)
>
> static void xen_post_allocator_init(void);
>
> -static __init void xen_mapping_pagetable_reserve(u64 start, u64 end)
> -{
> - /* reserve the range used */
> - native_pagetable_reserve(start, end);
> -
> - /* set as RW the rest */
> - printk(KERN_DEBUG "xen: setting RW the range %llx - %llx\n", end,
> - PFN_PHYS(pgt_buf_top));
> - while (end < PFN_PHYS(pgt_buf_top)) {
> - make_lowmem_page_readwrite(__va(end));
> - end += PAGE_SIZE;
> - }
> -}
> -
> #ifdef CONFIG_X86_64
> static void __init xen_cleanhighmap(unsigned long vaddr,
> unsigned long vaddr_end)
> @@ -1503,19 +1489,6 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte)
> #else /* CONFIG_X86_64 */
> static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte)
> {
> - unsigned long pfn = pte_pfn(pte);
> -
> - /*
> - * If the new pfn is within the range of the newly allocated
> - * kernel pagetable, and it isn't being mapped into an
> - * early_ioremap fixmap slot as a freshly allocated page, make sure
> - * it is RO.
> - */
> - if (((!is_early_ioremap_ptep(ptep) &&
> - pfn >= pgt_buf_start && pfn < pgt_buf_top)) ||
> - (is_early_ioremap_ptep(ptep) && pfn != (pgt_buf_end - 1)))
> - pte = pte_wrprotect(pte);
> -
> return pte;

you should just get rid of mask_rw_pte completely


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