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Date:      Fri, 31 May 2019 19:13:31 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org
Subject:   svn commit: r348479 - in stable/12/sys: amd64/amd64 i386/i386
Message-ID:  <201905311913.x4VJDV8f014200@repo.freebsd.org>
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Author: kib
Date: Fri May 31 19:13:31 2019
New Revision: 348479
URL: https://svnweb.freebsd.org/changeset/base/348479

Log:
  MFC r348246:
  Fix a corner case in demotion of kernel mappings.

Modified:
  stable/12/sys/amd64/amd64/pmap.c
  stable/12/sys/i386/i386/pmap.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/amd64/amd64/pmap.c
==============================================================================
--- stable/12/sys/amd64/amd64/pmap.c	Fri May 31 19:09:56 2019	(r348478)
+++ stable/12/sys/amd64/amd64/pmap.c	Fri May 31 19:13:31 2019	(r348479)
@@ -4167,8 +4167,10 @@ pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, v
 			    " in pmap %p", va, pmap);
 			return (FALSE);
 		}
-		if (va < VM_MAXUSER_ADDRESS)
+		if (va < VM_MAXUSER_ADDRESS) {
+			mpte->wire_count = NPTEPG;
 			pmap_resident_count_inc(pmap, 1);
+		}
 	}
 	mptepa = VM_PAGE_TO_PHYS(mpte);
 	firstpte = (pt_entry_t *)PHYS_TO_DMAP(mptepa);
@@ -4181,12 +4183,12 @@ pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, v
 	newpte = pmap_swap_pat(pmap, newpte);
 
 	/*
-	 * If the page table page is new, initialize it.
+	 * If the page table page is not leftover from an earlier promotion,
+	 * initialize it.
 	 */
-	if (mpte->wire_count == 1) {
-		mpte->wire_count = NPTEPG;
+	if ((oldpde & PG_PROMOTED) == 0)
 		pmap_fill_ptp(firstpte, newpte);
-	}
+
 	KASSERT((*firstpte & PG_FRAME) == (newpte & PG_FRAME),
 	    ("pmap_demote_pde: firstpte and newpte map different physical"
 	    " addresses"));

Modified: stable/12/sys/i386/i386/pmap.c
==============================================================================
--- stable/12/sys/i386/i386/pmap.c	Fri May 31 19:09:56 2019	(r348478)
+++ stable/12/sys/i386/i386/pmap.c	Fri May 31 19:13:31 2019	(r348479)
@@ -2845,8 +2845,10 @@ pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offse
 			    " in pmap %p", va, pmap);
 			return (FALSE);
 		}
-		if (pmap != kernel_pmap)
+		if (pmap != kernel_pmap) {
+			mpte->wire_count = NPTEPG;
 			pmap->pm_stats.resident_count++;
+		}
 	}
 	mptepa = VM_PAGE_TO_PHYS(mpte);
 
@@ -2894,12 +2896,12 @@ pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offse
 		newpte ^= PG_PDE_PAT | PG_PTE_PAT;
 
 	/*
-	 * If the page table page is new, initialize it.
+	 * If the page table page is not leftover from an earlier promotion,
+	 * initialize it.
 	 */
-	if (mpte->wire_count == 1) {
-		mpte->wire_count = NPTEPG;
+	if ((oldpde & PG_PROMOTED) == 0)
 		pmap_fill_ptp(firstpte, newpte);
-	}
+
 	KASSERT((*firstpte & PG_FRAME) == (newpte & PG_FRAME),
 	    ("pmap_demote_pde: firstpte and newpte map different physical"
 	    " addresses"));

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