Author: markj
Date: Wed Oct 16 15:50:12 2019
New Revision: 353650
URL: https://svnweb.freebsd.org/changeset/base/353650

Log:
  Clear PGA_WRITEABLE in moea_pvo_remove().
  
  moea_pvo_remove() might remove the last mapping of a page, in which case
  it is clearly no longer writeable.  This can happen via pmap_remove(),
  or when a CoW fault removes the last mapping of the old page.
  
  Reported and tested by:       bdragon
  Reviewed by:  alc, bdragon, kib
  MFC after:    1 week
  Sponsored by: The FreeBSD Foundation
  Differential Revision:        https://reviews.freebsd.org/D22044

Modified:
  head/sys/powerpc/aim/mmu_oea.c

Modified: head/sys/powerpc/aim/mmu_oea.c
==============================================================================
--- head/sys/powerpc/aim/mmu_oea.c      Wed Oct 16 15:21:05 2019        
(r353649)
+++ head/sys/powerpc/aim/mmu_oea.c      Wed Oct 16 15:50:12 2019        
(r353650)
@@ -2108,23 +2108,26 @@ moea_pvo_remove(struct pvo_entry *pvo, int pteidx)
                pvo->pvo_pmap->pm_stats.wired_count--;
 
        /*
+        * Remove this PVO from the PV and pmap lists.
+        */
+       LIST_REMOVE(pvo, pvo_vlink);
+       RB_REMOVE(pvo_tree, &pvo->pvo_pmap->pmap_pvo, pvo);
+
+       /*
         * Save the REF/CHG bits into their cache if the page is managed.
+        * Clear PGA_WRITEABLE if all mappings of the page have been removed.
         */
        if ((pvo->pvo_vaddr & PVO_MANAGED) == PVO_MANAGED) {
-               struct  vm_page *pg;
+               struct vm_page *pg;
 
                pg = PHYS_TO_VM_PAGE(pvo->pvo_pte.pte.pte_lo & PTE_RPGN);
                if (pg != NULL) {
                        moea_attr_save(pg, pvo->pvo_pte.pte.pte_lo &
                            (PTE_REF | PTE_CHG));
+                       if (LIST_EMPTY(&pg->md.mdpg_pvoh))
+                               vm_page_aflag_clear(pg, PGA_WRITEABLE);
                }
        }
-
-       /*
-        * Remove this PVO from the PV and pmap lists.
-        */
-       LIST_REMOVE(pvo, pvo_vlink);
-       RB_REMOVE(pvo_tree, &pvo->pvo_pmap->pmap_pvo, pvo);
 
        /*
         * Remove this from the overflow list and return it to the pool
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