From: Rik van Riel <riel@redhat.com>
Date: Fri, 21 Nov 2008 14:31:19 -0500
Subject: [agp] use contiguous memory to support xen
Message-id: 20081121143119.7fd9d2df@cuia.bos.redhat.com
O-Subject: [RHEL5.3 PATCH 2/3] linux-xen: use contiguous memory for AGP
Bugzilla: 412691
RH-Acked-by: Don Dutile <ddutile@redhat.com>
RH-Acked-by: Bill Burns <bburns@redhat.com>
RH-Acked-by: Chris Lalancette <clalance@redhat.com>

X points the video card at chunks of physically contiguous memory.
The problem is that, under Xen, there is no guarantee about physical
memory layout and several "physically contiguous" kernel pages may
in fact be backed by non-contiguous machine physical memory.

The fix is to call xen_create_contiguous_region(), which makes the
hypervisor rearrange physical memory so there is an actual contiguous
range of pages backing kernel memory.

This is a backport of the following patches, with RHEL5 kABI
considerations thrown in:

http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/02a46885bd90

http://lkml.org/lkml/2007/4/2/186

Fixes bug 412691

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Jan Beulich <jbeulich@novell.com>

diff --git a/drivers/char/agp/ali-agp.c b/drivers/char/agp/ali-agp.c
index 5a31ec7..94b1a9f 100644
--- a/drivers/char/agp/ali-agp.c
+++ b/drivers/char/agp/ali-agp.c
@@ -145,6 +145,7 @@ static void *m1541_alloc_page(struct agp_bridge_data *bridge)
 	void *addr = agp_generic_alloc_page(agp_bridge);
 	u32 temp;
 
+	global_flush_tlb();
 	if (!addr)
 		return NULL;
 
@@ -160,6 +161,7 @@ static void ali_destroy_page(void * addr)
 	if (addr) {
 		global_cache_flush();	/* is this really needed?  --hch */
 		agp_generic_destroy_page(addr);
+		global_flush_tlb();
 	}
 }
 
diff --git a/drivers/char/agp/generic.c b/drivers/char/agp/generic.c
index 8824632..753de52 100644
--- a/drivers/char/agp/generic.c
+++ b/drivers/char/agp/generic.c
@@ -54,10 +54,13 @@ EXPORT_SYMBOL_GPL(agp_memory_reserved);
 #if defined(CONFIG_X86)
 int map_page_into_agp(struct page *page)
 {
-	int i;
-	i = change_page_attr(page, 1, PAGE_KERNEL_NOCACHE);
-	/* Caller's responsibility to call global_flush_tlb() for
-	 * performance reasons */
+	int i = 0;
+#ifdef CONFIG_XEN
+	if (!xen_create_contiguous_region((unsigned long)page_address(page), 0, 32))
+#endif
+		i = change_page_attr(page, 1, PAGE_KERNEL_NOCACHE);
+		/* Caller's responsibility to call global_flush_tlb() for
+		 * performance reasons */
 	return i;
 }
 EXPORT_SYMBOL_GPL(map_page_into_agp);
@@ -65,6 +68,9 @@ EXPORT_SYMBOL_GPL(map_page_into_agp);
 int unmap_page_from_agp(struct page *page)
 {
 	int i;
+#ifdef CONFIG_XEN
+	xen_destroy_contiguous_region((unsigned long)page_address(page), 0);
+#endif
 	i = change_page_attr(page, 1, PAGE_KERNEL);
 	/* Caller's responsibility to call global_flush_tlb() for
 	 * performance reasons */
diff --git a/drivers/char/agp/intel-agp.c b/drivers/char/agp/intel-agp.c
index f72fe60..8cbcea5 100644
--- a/drivers/char/agp/intel-agp.c
+++ b/drivers/char/agp/intel-agp.c
@@ -223,9 +223,17 @@ static void *i8xx_alloc_pages(void)
 	if (page == NULL)
 		return NULL;
 
+#ifdef CONFIG_XEN
+	if (xen_create_contiguous_region((unsigned long)page_address(page), 2, 32)) {
+		__free_pages(page, 2);
+		return NULL;
+	}
+#endif
+
 	if (change_page_attr(page, 4, PAGE_KERNEL_NOCACHE) < 0) {
+		change_page_attr(page, 4, PAGE_KERNEL);
 		global_flush_tlb();
-		__free_page(page);
+		__free_pages(page, 2);
 		return NULL;
 	}
 	global_flush_tlb();
@@ -245,9 +253,12 @@ static void i8xx_destroy_pages(void *addr)
 	page = virt_to_page(addr);
 	change_page_attr(page, 4, PAGE_KERNEL);
 	global_flush_tlb();
+#ifdef CONFIG_XEN
+	xen_destroy_contiguous_region((unsigned long)page_address(page), 2);
+#endif
 	put_page(page);
 	unlock_page(page);
-	free_pages((unsigned long)addr, 2);
+	__free_pages(page, 2);
 	atomic_dec(&agp_bridge->current_memory_agp);
 }