===== arch/ia64/pci/pci.c 1.65 vs edited =====
--- 1.65/arch/ia64/pci/pci.c	2005-01-12 10:08:48 -08:00
+++ edited/arch/ia64/pci/pci.c	2005-01-19 11:09:32 -08:00
@@ -539,7 +539,8 @@
 	 */
 	vma->vm_flags |= (VM_SHM | VM_RESERVED | VM_IO);
 
-	if (write_combine)
+	if (write_combine && efi_range_is_wc(vma->vm_start,
+					     vma->vm_end - vma->vm_start))
 		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
 	else
 		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
===== drivers/char/drm/drm_vm.c 1.36 vs edited =====
--- 1.36/drivers/char/drm/drm_vm.c	2004-11-04 02:35:43 -08:00
+++ edited/drivers/char/drm/drm_vm.c	2005-01-19 14:31:47 -08:00
@@ -612,8 +612,13 @@
 			vma->vm_flags |= VM_IO;	/* not in core dump */
 		}
 #if defined(__ia64__)
-		if (map->type != _DRM_AGP)
-			vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+		if (efi_range_is_wc(vma->vm_start, vma->vm_end -
+				    vma->vm_start))
+			vma->vm_page_prot =
+				pgprot_writecombine(vma->vm_page_prot);
+		else
+			vma->vm_page_prot =
+				pgprot_noncached(vma->vm_page_prot);
 #endif
 		offset = dev->driver->get_reg_ofs(dev);
 #ifdef __sparc__
===== drivers/video/fbmem.c 1.148 vs edited =====
--- 1.148/drivers/video/fbmem.c	2005-01-05 15:46:41 -08:00
+++ edited/drivers/video/fbmem.c	2005-01-19 14:52:06 -08:00
@@ -35,6 +35,7 @@
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/device.h>
+#include <linux/efi.h>
 
 #if defined(__mc68000__) || defined(CONFIG_APUS)
 #include <asm/setup.h>
@@ -950,9 +951,13 @@
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 #elif defined(__hppa__)
 	pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE;
-#elif defined(__ia64__) || defined(__arm__) || defined(__sh__) || \
-      defined(__m32r__)
+#elif defined(__arm__) || defined(__sh__) || defined(__m32r__)
 	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+#elif defined(__ia64__)
+	if (efi_range_is_wc(vma->vm_start, vma->vm_end - vma->vm_start))
+		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+	else
+		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 #else
 #warning What do we have to do here??
 #endif
===== include/linux/efi.h 1.12 vs edited =====
--- 1.12/include/linux/efi.h	2004-11-18 23:03:10 -08:00
+++ edited/include/linux/efi.h	2005-01-19 14:04:14 -08:00
@@ -305,6 +305,27 @@
 extern int __init efi_set_rtc_mmss(unsigned long nowtime);
 extern struct efi_memory_map memmap;
 
+/**
+ * efi_range_is_wc - check the WC bit on an address range
+ * @start: starting kvirt address
+ * @len: length of range
+ *
+ * Consult the EFI memory map and make sure it's ok to set this range WC.
+ * Returns true or false.
+ */
+static inline int efi_range_is_wc(unsigned long start, unsigned long len)
+{
+	int i;
+
+	for (i = 0; i < len; i += (1UL << EFI_PAGE_SHIFT)) {
+		unsigned long paddr = __pa(start + i);
+		if (!(efi_mem_attributes(paddr) & EFI_MEMORY_WC))
+			return 0;
+	}
+	/* The range checked out */
+	return 1;
+}
+
 #ifdef CONFIG_EFI_PCDP
 extern int __init efi_setup_pcdp_console(char *);
 #endif