svn commit: r299082 - head/sys/amd64/amd64

[Alan Cox]

Author: alc
Date: Wed May  4 17:54:13 2016
New Revision: 299082
URL: https://svnweb.freebsd.org/changeset/base/299082

Log:
  Explain why pmap_copy(), pmap_enter_pde(), and pmap_enter_quick_locked()
  call pmap_invalidate_page() even though they are not destroying a leaf-
  level page table entry.
  
  Eliminate some bogus white-space characters in a comment.
  
  Reviewed by:	kib

Modified:
  head/sys/amd64/amd64/pmap.c

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Wed May  4 17:52:53 2016	(r299081)
+++ head/sys/amd64/amd64/pmap.c	Wed May  4 17:54:13 2016	(r299082)
@@ -4407,6 +4407,12 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t 
 		    lockp)) {
 			SLIST_INIT(&free);
 			if (pmap_unwire_ptp(pmap, va, mpde, &free)) {
+				/*
+				 * Although "va" is not mapped, paging-
+				 * structure caches could nonetheless have
+				 * entries that refer to the freed page table
+				 * pages.  Invalidate those entries.
+				 */
 				pmap_invalidate_page(pmap, va);
 				pmap_free_zero_pages(&free);
 			}
@@ -4584,6 +4590,12 @@ pmap_enter_quick_locked(pmap_t pmap, vm_
 		if (mpte != NULL) {
 			SLIST_INIT(&free);
 			if (pmap_unwire_ptp(pmap, va, mpte, &free)) {
+				/*
+				 * Although "va" is not mapped, paging-
+				 * structure caches could nonetheless have
+				 * entries that refer to the freed page table
+				 * pages.  Invalidate those entries.
+				 */
 				pmap_invalidate_page(pmap, va);
 				pmap_free_zero_pages(&free);
 			}
@@ -4967,6 +4979,14 @@ pmap_copy(pmap_t dst_pmap, pmap_t src_pm
 					SLIST_INIT(&free);
 					if (pmap_unwire_ptp(dst_pmap, addr,
 					    dstmpte, &free)) {
+						/*
+						 * Although "addr" is not
+						 * mapped, paging-structure
+						 * caches could nonetheless
+						 * have entries that refer to
+						 * the freed page table pages.
+						 * Invalidate those entries.
+						 */
 						pmap_invalidate_page(dst_pmap,
 						    addr);
 						pmap_free_zero_pages(&free);
@@ -5219,7 +5239,7 @@ pmap_page_is_mapped(vm_page_t m)
  * Destroy all managed, non-wired mappings in the given user-space
  * pmap.  This pmap cannot be active on any processor besides the
  * caller.
- *                                                                                
+ *
  * This function cannot be applied to the kernel pmap.  Moreover, it
  * is not intended for general use.  It is only to be used during
  * process termination.  Consequently, it can be implemented in ways