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Date:      Sun, 19 Jul 2009 21:40:19 +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: r195774 - in head/sys: amd64/amd64 i386/i386 i386/xen vm
Message-ID:  <200907192140.n6JLeJ5X054549@svn.freebsd.org>
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Author: alc
Date: Sun Jul 19 21:40:19 2009
New Revision: 195774
URL: http://svn.freebsd.org/changeset/base/195774

Log:
  Change the handling of fictitious pages by pmap_page_set_memattr() on
  amd64 and i386.  Essentially, fictitious pages provide a mechanism for
  creating aliases for either normal or device-backed pages.  Therefore,
  pmap_page_set_memattr() on a fictitious page needn't update the direct
  map or flush the cache.  Such actions are the responsibility of the
  "primary" instance of the page or the device driver that "owns" the
  physical address.  For example, these actions are already performed by
  pmap_mapdev().
  
  The device pager needn't restore the memory attributes on a fictitious
  page before releasing it.  It's now pointless.
  
  Add pmap_page_set_memattr() to the Xen pmap.
  
  Approved by:	re (kib)

Modified:
  head/sys/amd64/amd64/pmap.c
  head/sys/i386/i386/pmap.c
  head/sys/i386/xen/pmap.c
  head/sys/vm/device_pager.c

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Sun Jul 19 20:25:59 2009	(r195773)
+++ head/sys/amd64/amd64/pmap.c	Sun Jul 19 21:40:19 2009	(r195774)
@@ -4381,9 +4381,12 @@ pmap_page_set_memattr(vm_page_t m, vm_me
 	m->md.pat_mode = ma;
 
 	/*
-	 * Update the direct mapping and flush the cache.
+	 * If "m" is a normal page, update its direct mapping.  This update
+	 * can be relied upon to perform any cache operations that are
+	 * required for data coherence.
 	 */
-	if (pmap_change_attr(PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m)), PAGE_SIZE,
+	if ((m->flags & PG_FICTITIOUS) == 0 &&
+	    pmap_change_attr(PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m)), PAGE_SIZE,
 	    m->md.pat_mode))
 		panic("memory attribute change on the direct map failed");
 }

Modified: head/sys/i386/i386/pmap.c
==============================================================================
--- head/sys/i386/i386/pmap.c	Sun Jul 19 20:25:59 2009	(r195773)
+++ head/sys/i386/i386/pmap.c	Sun Jul 19 21:40:19 2009	(r195774)
@@ -4466,12 +4466,13 @@ pmap_page_set_memattr(vm_page_t m, vm_me
 	m->md.pat_mode = ma;
 
 	/*
-	 * Flush CPU caches to make sure any data isn't cached that shouldn't
-	 * be, etc.
+	 * If "m" is a normal page, flush it from the cache.
 	 */    
-	/* If "Self Snoop" is supported, do nothing. */
-	if (!(cpu_feature & CPUID_SS))
-		pmap_invalidate_cache();
+	if ((m->flags & PG_FICTITIOUS) == 0) {
+		/* If "Self Snoop" is supported, do nothing. */
+		if (!(cpu_feature & CPUID_SS))
+			pmap_invalidate_cache();
+	}
 }
 
 int

Modified: head/sys/i386/xen/pmap.c
==============================================================================
--- head/sys/i386/xen/pmap.c	Sun Jul 19 20:25:59 2009	(r195773)
+++ head/sys/i386/xen/pmap.c	Sun Jul 19 21:40:19 2009	(r195774)
@@ -3921,6 +3921,25 @@ pmap_unmapdev(vm_offset_t va, vm_size_t 
 	kmem_free(kernel_map, base, size);
 }
 
+/*
+ * Sets the memory attribute for the specified page.
+ */
+void
+pmap_page_set_memattr(vm_page_t m, vm_memattr_t ma)
+{
+
+	m->md.pat_mode = ma;
+
+	/*
+	 * If "m" is a normal page, flush it from the cache.
+	 */    
+	if ((m->flags & PG_FICTITIOUS) == 0) {
+		/* If "Self Snoop" is supported, do nothing. */
+		if (!(cpu_feature & CPUID_SS))
+			pmap_invalidate_cache();
+	}
+}
+
 int
 pmap_change_attr(va, size, mode)
 	vm_offset_t va;

Modified: head/sys/vm/device_pager.c
==============================================================================
--- head/sys/vm/device_pager.c	Sun Jul 19 20:25:59 2009	(r195773)
+++ head/sys/vm/device_pager.c	Sun Jul 19 21:40:19 2009	(r195774)
@@ -305,7 +305,8 @@ dev_pager_haspage(object, pindex, before
 
 /*
  * Create a fictitious page with the specified physical address and memory
- * attribute.
+ * attribute.  The memory attribute is the only the machine-dependent aspect
+ * of a fictitious page that must be initialized.
  */
 static vm_page_t
 dev_pager_getfake(vm_paddr_t paddr, vm_memattr_t memattr)
@@ -317,11 +318,9 @@ dev_pager_getfake(vm_paddr_t paddr, vm_m
 	/* Fictitious pages don't use "segind". */
 	m->flags = PG_FICTITIOUS;
 	/* Fictitious pages don't use "order" or "pool". */
-	pmap_page_init(m);
 	m->oflags = VPO_BUSY;
 	m->wire_count = 1;
-	if (memattr != VM_MEMATTR_DEFAULT)
-		pmap_page_set_memattr(m, memattr);
+	pmap_page_set_memattr(m, memattr);
 	return (m);
 }
 
@@ -334,9 +333,6 @@ dev_pager_putfake(vm_page_t m)
 
 	if (!(m->flags & PG_FICTITIOUS))
 		panic("dev_pager_putfake: bad page");
-	/* Restore the default memory attribute to "phys_addr". */
-	if (pmap_page_get_memattr(m) != VM_MEMATTR_DEFAULT)
-		pmap_page_set_memattr(m, VM_MEMATTR_DEFAULT);
 	uma_zfree(fakepg_zone, m);
 }
 
@@ -350,10 +346,6 @@ dev_pager_updatefake(vm_page_t m, vm_pad
 
 	if (!(m->flags & PG_FICTITIOUS))
 		panic("dev_pager_updatefake: bad page");
-	/* Restore the default memory attribute before changing "phys_addr". */
-	if (pmap_page_get_memattr(m) != VM_MEMATTR_DEFAULT)
-		pmap_page_set_memattr(m, VM_MEMATTR_DEFAULT);
 	m->phys_addr = paddr;
-	if (memattr != VM_MEMATTR_DEFAULT)
-		pmap_page_set_memattr(m, memattr);
+	pmap_page_set_memattr(m, memattr);
 }

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