[PATCH] AGP fix for Xen VMM

When Linux is running on the Xen virtual machine monitor, physical
addresses are virtualised and cannot be directly referenced by the AGP
GART.  This patch fixes the GART driver for Xen by adding a layer of
abstraction between physical addresses and 'GART addresses'.

Architecture-specific functions are also defined for allocating and freeing
the GATT.  Xen requires this to ensure that table really is contiguous from
the point of view of the GART.

These extra interface functions are defined as 'no-ops' for all existing
architectures that use the GART driver.

Signed-off-by: Keir Fraser <keir@xensource.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Dave Jones <davej@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/asm-x86_64/agp.h b/include/asm-x86_64/agp.h
index 0bb9019d58a..06c52ee9c06 100644
--- a/include/asm-x86_64/agp.h
+++ b/include/asm-x86_64/agp.h
@@ -19,4 +19,14 @@ int unmap_page_from_agp(struct page *page);
    worth it. Would need a page for it. */
 #define flush_agp_cache() asm volatile("wbinvd":::"memory")
 
+/* Convert a physical address to an address suitable for the GART. */
+#define phys_to_gart(x) (x)
+#define gart_to_phys(x) (x)
+
+/* GATT allocation. Returns/accepts GATT kernel virtual address. */
+#define alloc_gatt_pages(order)         \
+        ((char *)__get_free_pages(GFP_KERNEL, (order)))
+#define free_gatt_pages(table, order)   \
+        free_pages((unsigned long)(table), (order))
+
 #endif