[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>

4 files changed, 6 insertions, 4 deletions

diff --git a/arch/x86_64/kernel/aperture.c b/arch/x86_64/kernel/aperture.c
index c7f4fdd20f05..e4e2b7d01f89 100644
--- a/arch/x86_64/kernel/aperture.c
+++ b/arch/x86_64/kernel/aperture.c
@@ -23,6 +23,7 @@
 #include <asm/io.h>
 #include <asm/proto.h>
 #include <asm/pci-direct.h>
+#include <asm/dma.h>
 
 int iommu_aperture;
 int iommu_aperture_disabled __initdata = 0;
@@ -247,7 +248,7 @@ void __init iommu_hole_init(void)
                 /* Got the aperture from the AGP bridge */
         } else if (swiotlb && !valid_agp) {
                 /* Do nothing */
-        } else if ((!no_iommu && end_pfn >= 0xffffffff>>PAGE_SHIFT) ||
+        } else if ((!no_iommu && end_pfn >= MAX_DMA32_PFN) ||
                    force_iommu ||
                    valid_agp ||
                    fallback_aper_force) { 
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
diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c
index 2b865c90b041..116e00f1bb7b 100644
--- a/arch/x86_64/kernel/pci-gart.c
+++ b/arch/x86_64/kernel/pci-gart.c
@@ -804,7 +804,7 @@ static int __init pci_iommu_init(void)
         } 
         
         if (no_iommu ||
-            (!force_iommu && end_pfn < 0xffffffff>>PAGE_SHIFT) ||
+            (!force_iommu && (end_pfn-1) < 0xffffffff>>PAGE_SHIFT) ||
             !iommu_aperture ||
             (no_agp && init_k8_gatt(&info) < 0)) {
                 printk(KERN_INFO "PCI-DMA: Disabling IOMMU.\n"); 
diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index 1faae5fc1c01..5337ca0ea7b9 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -424,7 +424,7 @@ void __init mem_init(void)
 
 #ifdef CONFIG_SWIOTLB
         if (!iommu_aperture &&
-            (end_pfn >= 0xffffffff>>PAGE_SHIFT || force_iommu))
+            ((end_pfn-1) >= 0xffffffff>>PAGE_SHIFT || force_iommu))
                swiotlb = 1;
         if (swiotlb)
                 swiotlb_init();