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Date:      Thu, 19 Sep 2019 14:36:30 +0000 (UTC)
From:      Alan Cox <alc@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: r352517 - in stable/12/sys: amd64/amd64 i386/i386
Message-ID:  <201909191436.x8JEaU8O011817@repo.freebsd.org>
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Author: alc
Date: Thu Sep 19 14:36:30 2019
New Revision: 352517
URL: https://svnweb.freebsd.org/changeset/base/352517

Log:
  MFC r349526:
  
  When we protect PTEs (as opposed to PDEs), we only call vm_page_dirty()
  when, in fact, we are write protecting the page and the PTE has PG_M set.
  However, pmap_protect_pde() was always calling vm_page_dirty() when the PDE
  has PG_M set.  So, adding PG_NX to a writeable PDE could result in
  unnecessary (but harmless) calls to vm_page_dirty().
  
  Simplify the loop calling vm_page_dirty() in pmap_protect_pde().

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	Thu Sep 19 13:25:19 2019	(r352516)
+++ stable/12/sys/amd64/amd64/pmap.c	Thu Sep 19 14:36:30 2019	(r352517)
@@ -5214,8 +5214,7 @@ static boolean_t
 pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva, vm_prot_t prot)
 {
 	pd_entry_t newpde, oldpde;
-	vm_offset_t eva, va;
-	vm_page_t m;
+	vm_page_t m, mt;
 	boolean_t anychanged;
 	pt_entry_t PG_G, PG_M, PG_RW;
 
@@ -5229,15 +5228,15 @@ pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offs
 	anychanged = FALSE;
 retry:
 	oldpde = newpde = *pde;
-	if ((oldpde & (PG_MANAGED | PG_M | PG_RW)) ==
-	    (PG_MANAGED | PG_M | PG_RW)) {
-		eva = sva + NBPDR;
-		for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
-		    va < eva; va += PAGE_SIZE, m++)
-			vm_page_dirty(m);
-	}
-	if ((prot & VM_PROT_WRITE) == 0)
+	if ((prot & VM_PROT_WRITE) == 0) {
+		if ((oldpde & (PG_MANAGED | PG_M | PG_RW)) ==
+		    (PG_MANAGED | PG_M | PG_RW)) {
+			m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
+			for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
+				vm_page_dirty(mt);
+		}
 		newpde &= ~(PG_RW | PG_M);
+	}
 	if ((prot & VM_PROT_EXECUTE) == 0)
 		newpde |= pg_nx;
 	if (newpde != oldpde) {

Modified: stable/12/sys/i386/i386/pmap.c
==============================================================================
--- stable/12/sys/i386/i386/pmap.c	Thu Sep 19 13:25:19 2019	(r352516)
+++ stable/12/sys/i386/i386/pmap.c	Thu Sep 19 14:36:30 2019	(r352517)
@@ -3332,8 +3332,7 @@ static boolean_t
 pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva, vm_prot_t prot)
 {
 	pd_entry_t newpde, oldpde;
-	vm_offset_t eva, va;
-	vm_page_t m;
+	vm_page_t m, mt;
 	boolean_t anychanged;
 
 	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
@@ -3342,15 +3341,15 @@ pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offs
 	anychanged = FALSE;
 retry:
 	oldpde = newpde = *pde;
-	if ((oldpde & (PG_MANAGED | PG_M | PG_RW)) ==
-	    (PG_MANAGED | PG_M | PG_RW)) {
-		eva = sva + NBPDR;
-		for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
-		    va < eva; va += PAGE_SIZE, m++)
-			vm_page_dirty(m);
-	}
-	if ((prot & VM_PROT_WRITE) == 0)
+	if ((prot & VM_PROT_WRITE) == 0) {
+		if ((oldpde & (PG_MANAGED | PG_M | PG_RW)) ==
+		    (PG_MANAGED | PG_M | PG_RW)) {
+			m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
+			for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
+				vm_page_dirty(mt);
+		}
 		newpde &= ~(PG_RW | PG_M);
+	}
 #if defined(PAE) || defined(PAE_TABLES)
 	if ((prot & VM_PROT_EXECUTE) == 0)
 		newpde |= pg_nx;

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