2 files changed, 56 insertions, 15 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 4a5973abefc8..0db7303bccb6 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1187,8 +1187,6 @@ asmlinkage void __init xen_start_kernel(void)
         /* Allocate and initialize top and mid mfn levels for p2m structure */
         xen_build_mfn_list_list();
 
-        init_mm.pgd = pgd;
-
         /* keep using Xen gdt for now; no urgent need to change it */
 
 #ifdef CONFIG_X86_32
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 21ed8d7f75a5..c9cf23e17440 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -2119,44 +2119,83 @@ __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
         return pgd;
 }
 #else   /* !CONFIG_X86_64 */
-static RESERVE_BRK_ARRAY(pmd_t, level2_kernel_pgt, PTRS_PER_PMD);
+static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);
+static RESERVE_BRK_ARRAY(pmd_t, swapper_kernel_pmd, PTRS_PER_PMD);
+
+static __init void xen_write_cr3_init(unsigned long cr3)
+{
+        unsigned long pfn = PFN_DOWN(__pa(swapper_pg_dir));
+
+        BUG_ON(read_cr3() != __pa(initial_page_table));
+        BUG_ON(cr3 != __pa(swapper_pg_dir));
+
+        /*
+         * We are switching to swapper_pg_dir for the first time (from
+         * initial_page_table) and therefore need to mark that page
+         * read-only and then pin it.
+         *
+         * Xen disallows sharing of kernel PMDs for PAE
+         * guests. Therefore we must copy the kernel PMD from
+         * initial_page_table into a new kernel PMD to be used in
+         * swapper_pg_dir.
+         */
+        swapper_kernel_pmd =
+                extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
+        memcpy(swapper_kernel_pmd, initial_kernel_pmd,
+               sizeof(pmd_t) * PTRS_PER_PMD);
+        swapper_pg_dir[KERNEL_PGD_BOUNDARY] =
+                __pgd(__pa(swapper_kernel_pmd) | _PAGE_PRESENT);
+        set_page_prot(swapper_kernel_pmd, PAGE_KERNEL_RO);
+
+        set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
+        xen_write_cr3(cr3);
+        pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, pfn);
+
+        pin_pagetable_pfn(MMUEXT_UNPIN_TABLE,
+                          PFN_DOWN(__pa(initial_page_table)));
+        set_page_prot(initial_page_table, PAGE_KERNEL);
+        set_page_prot(initial_kernel_pmd, PAGE_KERNEL);
+
+        pv_mmu_ops.write_cr3 = &xen_write_cr3;
+}
 
 __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
                                          unsigned long max_pfn)
 {
         pmd_t *kernel_pmd;
 
-        level2_kernel_pgt = extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
+        initial_kernel_pmd =
+                extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
 
         max_pfn_mapped = PFN_DOWN(__pa(xen_start_info->pt_base) +
                                   xen_start_info->nr_pt_frames * PAGE_SIZE +
                                   512*1024);
 
         kernel_pmd = m2v(pgd[KERNEL_PGD_BOUNDARY].pgd);
-        memcpy(level2_kernel_pgt, kernel_pmd, sizeof(pmd_t) * PTRS_PER_PMD);
+        memcpy(initial_kernel_pmd, kernel_pmd, sizeof(pmd_t) * PTRS_PER_PMD);
 
-        xen_map_identity_early(level2_kernel_pgt, max_pfn);
+        xen_map_identity_early(initial_kernel_pmd, max_pfn);
 
-        memcpy(swapper_pg_dir, pgd, sizeof(pgd_t) * PTRS_PER_PGD);
-        set_pgd(&swapper_pg_dir[KERNEL_PGD_BOUNDARY],
-                        __pgd(__pa(level2_kernel_pgt) | _PAGE_PRESENT));
+        memcpy(initial_page_table, pgd, sizeof(pgd_t) * PTRS_PER_PGD);
+        initial_page_table[KERNEL_PGD_BOUNDARY] =
+                __pgd(__pa(initial_kernel_pmd) | _PAGE_PRESENT);
 
-        set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
-        set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
+        set_page_prot(initial_kernel_pmd, PAGE_KERNEL_RO);
+        set_page_prot(initial_page_table, PAGE_KERNEL_RO);
         set_page_prot(empty_zero_page, PAGE_KERNEL_RO);
 
         pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
 
-        xen_write_cr3(__pa(swapper_pg_dir));
-
-        pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, PFN_DOWN(__pa(swapper_pg_dir)));
+        pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE,
+                          PFN_DOWN(__pa(initial_page_table)));
+        xen_write_cr3(__pa(initial_page_table));
 
         memblock_x86_reserve_range(__pa(xen_start_info->pt_base),
                       __pa(xen_start_info->pt_base +
                            xen_start_info->nr_pt_frames * PAGE_SIZE),
                       "XEN PAGETABLES");
 
-        return swapper_pg_dir;
+        return initial_page_table;
 }
 #endif  /* CONFIG_X86_64 */
 
@@ -2290,7 +2329,11 @@ static const struct pv_mmu_ops xen_mmu_ops __initdata = {
         .write_cr2 = xen_write_cr2,
 
         .read_cr3 = xen_read_cr3,
+#ifdef CONFIG_X86_32
+        .write_cr3 = xen_write_cr3_init,
+#else
         .write_cr3 = xen_write_cr3,
+#endif
 
         .flush_tlb_user = xen_flush_tlb,
         .flush_tlb_kernel = xen_flush_tlb,