KVM: x86: Add is_executable_pte()

Extracted from commit d3e328f2cb "kvm: x86: mmu: Verify that
restored PTE has needed perms in fast page fault".

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kvm/mmu.c

@@ -338,6 +338,11 @@ static int is_last_spte(u64 pte, int level)
 	return 0;
 }
 
+static bool is_executable_pte(u64 spte)
+{
+	return (spte & (shadow_x_mask | shadow_nx_mask)) == shadow_x_mask;
+}
+
 static kvm_pfn_t spte_to_pfn(u64 pte)
 {
 	return (pte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;