nEPT: correctly check if remote tlb flush is needed for shadowed EPT tables

need_remote_flush() assumes that shadow page is in PT64 format, but
with addition of nested EPT this is no longer always true. Fix it by
bits definitions that depend on host shadow page type.
Reported-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.c

@@ -132,8 +132,8 @@ module_param(dbg, bool, 0644);
 	(PAGE_MASK & ~((1ULL << (PAGE_SHIFT + (((level) - 1) \
 					    * PT32_LEVEL_BITS))) - 1))
 
-#define PT64_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | PT_USER_MASK \
-			| PT64_NX_MASK)
+#define PT64_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | shadow_user_mask \
+			| shadow_x_mask | shadow_nx_mask)
 
 #define ACC_EXEC_MASK    1
 #define ACC_WRITE_MASK   PT_WRITABLE_MASK
@@ -3879,8 +3879,8 @@ static bool need_remote_flush(u64 old, u64 new)
 		return true;
 	if ((old ^ new) & PT64_BASE_ADDR_MASK)
 		return true;
-	old ^= PT64_NX_MASK;
-	new ^= PT64_NX_MASK;
+	old ^= shadow_nx_mask;
+	new ^= shadow_nx_mask;
 	return (old & ~new & PT64_PERM_MASK) != 0;
 }