3 files changed, 24 insertions, 8 deletions

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 30a3e977612..66aee6c4123 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -348,6 +348,7 @@ extern void __iomem *early_memremap(resource_size_t phys_addr,
                                     unsigned long size);
 extern void early_iounmap(void __iomem *addr, unsigned long size);
 extern void fixup_early_ioremap(void);
+extern bool is_early_ioremap_ptep(pte_t *ptep);
 
 #define IO_SPACE_LIMIT 0xffff
 
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 3ba6e0608c5..0369843511d 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -362,6 +362,11 @@ static inline pte_t * __init early_ioremap_pte(unsigned long addr)
         return &bm_pte[pte_index(addr)];
 }
 
+bool __init is_early_ioremap_ptep(pte_t *ptep)
+{
+        return ptep >= &bm_pte[0] && ptep < &bm_pte[PAGE_SIZE/sizeof(pte_t)];
+}
+
 static unsigned long slot_virt[FIX_BTMAPS_SLOTS] __initdata;
 
 void __init early_ioremap_init(void)
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 4fe04ac0bae..7d55e9ee3a7 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -56,6 +56,7 @@
 #include <asm/e820.h>
 #include <asm/linkage.h>
 #include <asm/page.h>
+#include <asm/init.h>
 
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
@@ -360,7 +361,8 @@ void make_lowmem_page_readonly(void *vaddr)
         unsigned int level;
 
         pte = lookup_address(address, &level);
-        BUG_ON(pte == NULL);
+        if (pte == NULL)
+                return;         /* vaddr missing */
 
         ptev = pte_wrprotect(*pte);
 
@@ -375,7 +377,8 @@ void make_lowmem_page_readwrite(void *vaddr)
         unsigned int level;
 
         pte = lookup_address(address, &level);
-        BUG_ON(pte == NULL);
+        if (pte == NULL)
+                return;         /* vaddr missing */
 
         ptev = pte_mkwrite(*pte);
 
@@ -1509,13 +1512,25 @@ static void xen_pgd_free(struct mm_struct *mm, pgd_t *pgd)
 #endif
 }
 
-#ifdef CONFIG_X86_32
 static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte)
 {
+        unsigned long pfn = pte_pfn(pte);
+
+#ifdef CONFIG_X86_32
         /* If there's an existing pte, then don't allow _PAGE_RW to be set */
         if (pte_val_ma(*ptep) & _PAGE_PRESENT)
                 pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) &
                                pte_val_ma(pte));
+#endif
+
+        /*
+         * 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.
+         */
+        if (!is_early_ioremap_ptep(ptep) &&
+            pfn >= e820_table_start && pfn < e820_table_end)
+                pte = pte_wrprotect(pte);
 
         return pte;
 }
@@ -1528,7 +1543,6 @@ static __init void xen_set_pte_init(pte_t *ptep, pte_t pte)
 
         xen_set_pte(ptep, pte);
 }
-#endif
 
 static void pin_pagetable_pfn(unsigned cmd, unsigned long pfn)
 {
@@ -1973,11 +1987,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initdata = {
         .alloc_pmd_clone = paravirt_nop,
         .release_pmd = xen_release_pmd_init,
 
-#ifdef CONFIG_X86_64
-        .set_pte = xen_set_pte,
-#else
         .set_pte = xen_set_pte_init,
-#endif
         .set_pte_at = xen_set_pte_at,
         .set_pmd = xen_set_pmd_hyper,