[PATCH] x86_64: Fix off by one in IOMMU check

Fix off by one when checking if the machine has enougn memory to need IOMMU
This caused the IOMMUs to be needlessly enabled for mem=4G

Based on a patch from Jon Mason

Signed-off-by: jdmason@us.ibm.com
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index bdc589924b10..83ea86e0633a 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -37,6 +37,7 @@
 #include <asm/proto.h>
 #include <asm/mach_apic.h>
 #include <asm/acpi.h>
+#include <asm/dma.h>
 
 #define __apicdebuginit  __init
 
@@ -281,7 +282,7 @@ void __init check_ioapic(void)
                                 switch (vendor) { 
                                 case PCI_VENDOR_ID_VIA:
 #ifdef CONFIG_GART_IOMMU
-                                        if ((end_pfn >= (0xffffffff>>PAGE_SHIFT) ||
+                                        if ((end_pfn > MAX_DMA32_PFN ||
                                              force_iommu) &&
                                             !iommu_aperture_allowed) {
                                                 printk(KERN_INFO