xen: mask unwanted pte bits in __supported_pte_mask

[ Stable: this isn't a bugfix in itself, but it's a pre-requiste
  for "xen: don't drop NX bit" ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>
Cc: the arch/x86 maintainers <x86@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index c8a56e4..c048de3 100644 (file)
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1228,6 +1228,11 @@ asmlinkage void __init xen_start_kernel(void)
        if (xen_feature(XENFEAT_supervisor_mode_kernel))
                pv_info.kernel_rpl = 0;
 
+       /* Prevent unwanted bits from being set in PTEs. */
+       __supported_pte_mask &= ~_PAGE_GLOBAL;
+       if (!is_initial_xendomain())
+               __supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);
+
        /* set the limit of our address space */
        xen_reserve_top();
 

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 3525ef5..3f2a67f 100644 (file)
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -199,10 +199,8 @@ pgdval_t xen_pgd_val(pgd_t pgd)
 
 pte_t xen_make_pte(pteval_t pte)
 {
-       if (pte & _PAGE_PRESENT) {
+       if (pte & _PAGE_PRESENT)
                pte = phys_to_machine(XPADDR(pte)).maddr;
-               pte &= ~(_PAGE_PCD | _PAGE_PWT);
-       }
 
        return (pte_t){ .pte = pte };
 }