[fedora-virt] [PATCH] xen: do not set NX bit when making initial pagetables readonly

[Ian Campbell <Ian Campbell citrix com>]

__supported_pte_mask has not been correctly configured at this point
and Xen prevents us from using the NX bit if the hardware does not
support it. Some BIOSes seem to offer the option to disable NX.

Signed-off-by: Ian Campbell <ian campbell citrix com>
Cc: Mark McLoughlin <markmc redhat com>
Cc: Jon Swanson <jswanson valuecommerce co jp>
Cc: fedora-virt redhat com
Cc: Jeremy Fitzhardinge <jeremy goop org>
Cc: Ingo Molnar <mingo elte hu>
---
 arch/x86/xen/enlighten.c |   24 +++++++++++++-----------
 1 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index bea2152..e705bdf 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -53,6 +53,8 @@
 #include "mmu.h"
 #include "multicalls.h"
 
+#define _KERNPG_TABLE_RO __pgprot(_KERNPG_TABLE & ~_PAGE_RW)
+
 EXPORT_SYMBOL_GPL(hypercall_page);
 
 DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
@@ -1487,9 +1489,9 @@ static __init void xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
 	}
 
 	for (pteidx = 0; pteidx < ident_pte; pteidx += PTRS_PER_PTE)
-		set_page_prot(&level1_ident_pgt[pteidx], PAGE_KERNEL_RO);
+		set_page_prot(&level1_ident_pgt[pteidx], _KERNPG_TABLE_RO);
 
-	set_page_prot(pmd, PAGE_KERNEL_RO);
+	set_page_prot(pmd, _KERNPG_TABLE_RO);
 }
 
 #ifdef CONFIG_X86_64
@@ -1543,12 +1545,12 @@ static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
 	xen_map_identity_early(level2_ident_pgt, max_pfn);
 
 	/* Make pagetable pieces RO */
-	set_page_prot(init_level4_pgt, PAGE_KERNEL_RO);
-	set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO);
-	set_page_prot(level3_kernel_pgt, PAGE_KERNEL_RO);
-	set_page_prot(level3_user_vsyscall, PAGE_KERNEL_RO);
-	set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
-	set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
+	set_page_prot(init_level4_pgt, _KERNPG_TABLE_RO);
+	set_page_prot(level3_ident_pgt, _KERNPG_TABLE_RO);
+	set_page_prot(level3_kernel_pgt, _KERNPG_TABLE_RO);
+	set_page_prot(level3_user_vsyscall, _KERNPG_TABLE_RO);
+	set_page_prot(level2_kernel_pgt, _KERNPG_TABLE_RO);
+	set_page_prot(level2_fixmap_pgt, _KERNPG_TABLE_RO);
 
 	/* Pin down new L4 */
 	pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,
@@ -1597,9 +1599,9 @@ static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
 	set_pgd(&swapper_pg_dir[KERNEL_PGD_BOUNDARY],
 			__pgd(__pa(level2_kernel_pgt) | _PAGE_PRESENT));
 
-	set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
-	set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
-	set_page_prot(empty_zero_page, PAGE_KERNEL_RO);
+	set_page_prot(level2_kernel_pgt, _KERNPG_TABLE_RO);
+	set_page_prot(swapper_pg_dir, _KERNPG_TABLE_RO);
+	set_page_prot(empty_zero_page, _KERNPG_TABLE_RO);
 
 	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
 
-- 
1.5.6.5