From: Ben Hutchings <ben@decadent.org.uk>
Date: Thu, 16 Mar 2017 03:05:43 +0000
Subject: [amd64] Don't WARN about expected W+X pages on Xen
Bug-Debian: https://bugs.debian.org/852324
Forwarded: not-needed

Currently Xen PV domains (or at least dom0) on amd64 tend to have a
large number of low kernel pages with W+X permissions.  It's not
obvious how to fix this, and we're not going to get any new
information by WARNing about this, but we do still want to hear about
other W+X cases.  So add a condition to the WARN_ON.

---
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>
+#include <xen/xen.h>
 
 #include <asm/kasan.h>
 #include <asm/pgtable.h>
@@ -220,7 +221,7 @@ static void note_page(struct seq_file *m
 		pgprotval_t pr = pgprot_val(st->current_prot);
 
 		if (st->check_wx && (pr & _PAGE_RW) && !(pr & _PAGE_NX)) {
-			WARN_ONCE(1,
+			WARN_ONCE(!(IS_ENABLED(CONFIG_X86_64) && xen_pv_domain()),
 				  "x86/mm: Found insecure W+X mapping at address %p/%pS\n",
 				  (void *)st->start_address,
 				  (void *)st->start_address);