svn commit: r305071 - head/sys/arm64/arm64

[Andrew Turner]

Author: andrew
Date: Tue Aug 30 16:45:15 2016
New Revision: 305071
URL: https://svnweb.freebsd.org/changeset/base/305071

Log:
  Because we need to use a break-before-make sequence when promoting pages
  there is a short period where functions that walk the kernel page table
  without locking them may see an invalid entry. One solution would be to add
  locking to these functions, however some may be called from locations where
  we are unable to sleep.
  
  Until a better solution can be found stop promoting pages in the kernel
  pmap so these functions work as expected.
  
  Obtained from:	ABT Systems Ltd
  MFC after:	1 month
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/arm64/arm64/pmap.c

Modified: head/sys/arm64/arm64/pmap.c
==============================================================================
--- head/sys/arm64/arm64/pmap.c	Tue Aug 30 16:43:24 2016	(r305070)
+++ head/sys/arm64/arm64/pmap.c	Tue Aug 30 16:45:15 2016	(r305071)
@@ -2936,14 +2936,17 @@ validate:
 	PTE_SYNC(l3);
 	pmap_invalidate_page(pmap, va);
 
-	if ((pmap != pmap_kernel()) && (pmap == &curproc->p_vmspace->vm_pmap))
-	    cpu_icache_sync_range(va, PAGE_SIZE);
-
-	if ((mpte == NULL || mpte->wire_count == NL3PG) &&
-	    pmap_superpages_enabled() && (m->flags & PG_FICTITIOUS) == 0 &&
-	    vm_reserv_level_iffullpop(m) == 0) {
-		KASSERT(lvl == 2, ("Invalid pde level %d", lvl));
-		pmap_promote_l2(pmap, pde, va, &lock);
+	if (pmap != pmap_kernel()) {
+		if (pmap == &curproc->p_vmspace->vm_pmap)
+		    cpu_icache_sync_range(va, PAGE_SIZE);
+
+		if ((mpte == NULL || mpte->wire_count == NL3PG) &&
+		    pmap_superpages_enabled() &&
+		    (m->flags & PG_FICTITIOUS) == 0 &&
+		    vm_reserv_level_iffullpop(m) == 0) {
+			KASSERT(lvl == 2, ("Invalid pde level %d", lvl));
+			pmap_promote_l2(pmap, pde, va, &lock);
+		}
 	}
 
 	if (lock != NULL)