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Date:      Fri, 13 Jul 2018 17:12:50 +0000 (UTC)
From:      Alan Cox <alc@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r336248 - head/sys/mips/mips
Message-ID:  <201807131712.w6DHCocI004265@repo.freebsd.org>
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Author: alc
Date: Fri Jul 13 17:12:50 2018
New Revision: 336248
URL: https://svnweb.freebsd.org/changeset/base/336248

Log:
  Invalidate the mapping before updating its physical address.
  
  Doing so ensures that all threads sharing the pmap have a consistent
  view of the mapping.  This fixes the problem described in the commit
  log message for r329254 without the overhead of an extra fault in the
  common case.  (Once the riscv pmap_enter() implementation is similarly
  modified, the workaround added in r329254 can be removed, reducing the
  overhead of CoW faults.)
  
  See also r335784 for amd64.  The mips implementation of pmap_enter()
  already reused the PV entry from the old mapping.
  
  Reviewed by:	kib, markj
  MFC after:	3 weeks
  Differential Revision:	https://reviews.freebsd.org/D16199

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

Modified: head/sys/mips/mips/pmap.c
==============================================================================
--- head/sys/mips/mips/pmap.c	Fri Jul 13 16:43:29 2018	(r336247)
+++ head/sys/mips/mips/pmap.c	Fri Jul 13 17:12:50 2018	(r336248)
@@ -2037,6 +2037,8 @@ pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, v
 	if (is_kernel_pmap(pmap))
 		newpte |= PTE_G;
 	PMAP_PTE_SET_CACHE_BITS(newpte, pa, m);
+	if ((m->oflags & VPO_UNMANAGED) == 0)
+		newpte |= PTE_MANAGED;
 
 	mpte = NULL;
 
@@ -2066,8 +2068,11 @@ pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, v
 		panic("pmap_enter: invalid page directory, pdir=%p, va=%p",
 		    (void *)pmap->pm_segtab, (void *)va);
 	}
-	om = NULL;
+
 	origpte = *pte;
+	KASSERT(!pte_test(&origpte, PTE_D | PTE_RO | PTE_V),
+	    ("pmap_enter: modified page not writable: va: %p, pte: %#jx",
+	    (void *)va, (uintmax_t)origpte));
 	opa = TLBLO_PTE_TO_PA(origpte);
 
 	/*
@@ -2086,10 +2091,6 @@ pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, v
 		    PTE_W))
 			pmap->pm_stats.wired_count--;
 
-		KASSERT(!pte_test(&origpte, PTE_D | PTE_RO),
-		    ("%s: modified page not writable: va: %p, pte: %#jx",
-		    __func__, (void *)va, (uintmax_t)origpte));
-
 		/*
 		 * Remove extra pte reference
 		 */
@@ -2098,8 +2099,6 @@ pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, v
 
 		if (pte_test(&origpte, PTE_MANAGED)) {
 			m->md.pv_flags |= PV_TABLE_REF;
-			om = m;
-			newpte |= PTE_MANAGED;
 			if (!pte_test(&newpte, PTE_RO))
 				vm_page_aflag_set(m, PGA_WRITEABLE);
 		}
@@ -2113,13 +2112,29 @@ pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, v
 	 * handle validating new mapping.
 	 */
 	if (opa) {
+		if (is_kernel_pmap(pmap))
+			*pte = PTE_G;
+		else
+			*pte = 0;
 		if (pte_test(&origpte, PTE_W))
 			pmap->pm_stats.wired_count--;
-
 		if (pte_test(&origpte, PTE_MANAGED)) {
 			om = PHYS_TO_VM_PAGE(opa);
+			if (pte_test(&origpte, PTE_D))
+				vm_page_dirty(om);
+			if ((om->md.pv_flags & PV_TABLE_REF) != 0) {
+				om->md.pv_flags &= ~PV_TABLE_REF;
+				vm_page_aflag_set(om, PGA_REFERENCED);
+			}
 			pv = pmap_pvh_remove(&om->md, pmap, va);
+			if (!pte_test(&newpte, PTE_MANAGED))
+				free_pv_entry(pmap, pv);
+			if ((om->aflags & PGA_WRITEABLE) != 0 &&
+			    TAILQ_EMPTY(&om->md.pv_list))
+				vm_page_aflag_clear(om, PGA_WRITEABLE);
 		}
+		pmap_invalidate_page(pmap, va);
+		origpte = 0;
 		if (mpte != NULL) {
 			mpte->wire_count--;
 			KASSERT(mpte->wire_count > 0,
@@ -2132,17 +2147,16 @@ pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, v
 	/*
 	 * Enter on the PV list if part of our managed memory.
 	 */
-	if ((m->oflags & VPO_UNMANAGED) == 0) {
+	if (pte_test(&newpte, PTE_MANAGED)) {
 		m->md.pv_flags |= PV_TABLE_REF;
-		if (pv == NULL)
+		if (pv == NULL) {
 			pv = get_pv_entry(pmap, FALSE);
-		pv->pv_va = va;
+			pv->pv_va = va;
+		}
 		TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
-		newpte |= PTE_MANAGED;
 		if (!pte_test(&newpte, PTE_RO))
 			vm_page_aflag_set(m, PGA_WRITEABLE);
-	} else if (pv != NULL)
-		free_pv_entry(pmap, pv);
+	}
 
 	/*
 	 * Increment counters
@@ -2163,21 +2177,11 @@ validate:
 	if (origpte != newpte) {
 		*pte = newpte;
 		if (pte_test(&origpte, PTE_V)) {
-			if (pte_test(&origpte, PTE_MANAGED) && opa != pa) {
-				if (om->md.pv_flags & PV_TABLE_REF)
-					vm_page_aflag_set(om, PGA_REFERENCED);
-				om->md.pv_flags &= ~PV_TABLE_REF;
-			}
+			KASSERT(opa == pa, ("pmap_enter: invalid update"));
 			if (pte_test(&origpte, PTE_D)) {
-				KASSERT(!pte_test(&origpte, PTE_RO),
-				    ("pmap_enter: modified page not writable:"
-				    " va: %p, pte: %#jx", (void *)va, (uintmax_t)origpte));
 				if (pte_test(&origpte, PTE_MANAGED))
-					vm_page_dirty(om);
+					vm_page_dirty(m);
 			}
-			if (pte_test(&origpte, PTE_MANAGED) &&
-			    TAILQ_EMPTY(&om->md.pv_list))
-				vm_page_aflag_clear(om, PGA_WRITEABLE);
 			pmap_update_page(pmap, va, newpte);
 		}
 	}

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