x86: CPA return early when requested feature is not available

Mask out the not supported bits (e.g. NX). If the clr/set masks
are empty after the mask return without changing anything.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 12 insertions, 2 deletions

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index a629cea5e465..f60b93dc2e57 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -405,8 +405,18 @@ static int __change_page_attr_set_clr(unsigned long addr, int numpages,
 static int change_page_attr_set_clr(unsigned long addr, int numpages,
                                     pgprot_t mask_set, pgprot_t mask_clr)
 {
-        int ret = __change_page_attr_set_clr(addr, numpages, mask_set,
-                                             mask_clr);
+        int ret;
+
+        /*
+         * Check, if we are requested to change a not supported
+         * feature:
+         */
+        mask_set = canon_pgprot(mask_set);
+        mask_clr = canon_pgprot(mask_clr);
+        if (!pgprot_val(mask_set) && !pgprot_val(mask_clr))
+                return 0;
+
+        ret = __change_page_attr_set_clr(addr, numpages, mask_set, mask_clr);
 
         /*
          * On success we use clflush, when the CPU supports it to