From d8aa5ec3382e6a545b8f25178d1e0992d4927f19 Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Wed, 9 Mar 2011 14:22:05 +0000 Subject: [PATCH] xen: update mask_rw_pte after kernel page tables init changes After "x86-64, mm: Put early page table high" already existing kernel page table pages can be mapped using early_ioremap too so we need to update mask_rw_pte to make sure these pages are still mapped RO. The reason why we have to do that is explain by the commit message of fef5ba797991f9335bcfc295942b684f9bf613a1: "Xen requires that all pages containing pagetable entries to be mapped read-only. If pages used for the initial pagetable are already mapped then we can change the mapping to RO. However, if they are initially unmapped, we need to make sure that when they are later mapped, they are also mapped RO. ..SNIP.. the pagetable setup code early_ioremaps the pages to write their entries, so we must make sure that mappings created in the early_ioremap fixmap area are mapped RW. (Those mappings are removed before the pages are presented to Xen as pagetable pages.)" We accomplish all this in mask_rw_pte by mapping RO all the pages mapped using early_ioremap apart from the last one that has been allocated because it is not a page table page yet (it has not been hooked into the page tables yet). Signed-off-by: Stefano Stabellini Acked-by: Konrad Rzeszutek Wilk LKML-Reference: Signed-off-by: H. Peter Anvin --- arch/x86/xen/mmu.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 6e27979506c..21058ad1e5e 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -1488,10 +1488,12 @@ static __init pte_t mask_rw_pte(pte_t *ptep, pte_t 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, make sure it is RO. + * 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_end) + if (((!is_early_ioremap_ptep(ptep) && + pfn >= pgt_buf_start && pfn < pgt_buf_end)) || + (is_early_ioremap_ptep(ptep) && pfn != (pgt_buf_end - 1))) pte = pte_wrprotect(pte); return pte; -- 2.20.1