4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Boris Ostrovsky <[email protected]>

commit 31ad7f8e7dc94d3b85ccf9b6141ce6dfd35a1781 upstream.

Writing to it directly does not work for Xen PV guests.

Fixes: 49275fef986a ("x86/vsyscall/64: Explicitly set _PAGE_USER in the 
pagetable hierarchy")
Signed-off-by: Boris Ostrovsky <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Acked-by: Andy Lutomirski <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 arch/x86/entry/vsyscall/vsyscall_64.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -355,7 +355,7 @@ void __init set_vsyscall_pgtable_user_bi
        set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER));
        p4d = p4d_offset(pgd, VSYSCALL_ADDR);
 #if CONFIG_PGTABLE_LEVELS >= 5
-       p4d->p4d |= _PAGE_USER;
+       set_p4d(p4d, __p4d(p4d_val(*p4d) | _PAGE_USER));
 #endif
        pud = pud_offset(p4d, VSYSCALL_ADDR);
        set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER));


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