5 files changed, 10 insertions, 1 deletions

diff --git a/arch/x86_64/kernel/aperture.c b/arch/x86_64/kernel/aperture.c
index 9ea723bab16c..a195ef06ec55 100644
--- a/arch/x86_64/kernel/aperture.c
+++ b/arch/x86_64/kernel/aperture.c
@@ -209,6 +209,7 @@ void __init iommu_hole_init(void)
                 if (!early_is_k8_nb(read_pci_config(0, num, 3, 0x00)))
                         continue;
 
+                iommu_detected = 1;
                 iommu_aperture = 1; 
 
                 aper_order = (read_pci_config(0, num, 3, 0x90) >> 1) & 7; 
diff --git a/arch/x86_64/kernel/pci-dma.c b/arch/x86_64/kernel/pci-dma.c
index 33926c367250..7edd1a40fab3 100644
--- a/arch/x86_64/kernel/pci-dma.c
+++ b/arch/x86_64/kernel/pci-dma.c
@@ -33,6 +33,9 @@ int panic_on_overflow __read_mostly = 0;
 int force_iommu __read_mostly= 0;
 #endif
 
+/* Set this to 1 if there is a HW IOMMU in the system */
+int iommu_detected __read_mostly = 0;
+
 /* Dummy device used for NULL arguments (normally ISA). Better would
    be probably a smaller DMA mask, but this is bug-to-bug compatible
    to i386. */
diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c
index 82a346e6e2e4..4f67957d2b42 100644
--- a/arch/x86_64/kernel/pci-gart.c
+++ b/arch/x86_64/kernel/pci-gart.c
@@ -597,6 +597,10 @@ static int __init pci_iommu_init(void)
         if (swiotlb)
                 return -ENODEV;
 
+        /* Did we detect a different HW IOMMU? */
+        if (iommu_detected && !iommu_aperture)
+                return -1;
+
         if (no_iommu ||
             (!force_iommu && end_pfn <= MAX_DMA32_PFN) ||
             !iommu_aperture ||
diff --git a/arch/x86_64/kernel/pci-swiotlb.c b/arch/x86_64/kernel/pci-swiotlb.c
index 990ed67896f2..ebdb77fe2057 100644
--- a/arch/x86_64/kernel/pci-swiotlb.c
+++ b/arch/x86_64/kernel/pci-swiotlb.c
@@ -31,7 +31,7 @@ struct dma_mapping_ops swiotlb_dma_ops = {
 void pci_swiotlb_init(void)
 {
         /* don't initialize swiotlb if iommu=off (no_iommu=1) */
-        if (!iommu_aperture && !no_iommu &&
+        if (!iommu_detected && !no_iommu &&
             (end_pfn > MAX_DMA32_PFN || force_iommu))
                swiotlb = 1;
         if (swiotlb) {
diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
index 105476ff8039..9d3335b4e9b6 100644
--- a/include/asm-x86_64/proto.h
+++ b/include/asm-x86_64/proto.h
@@ -116,6 +116,7 @@ extern int skip_ioapic_setup;
 extern int acpi_ht;
 extern int acpi_disabled;
 
+extern int iommu_detected;
 #ifdef CONFIG_IOMMU
 extern int fallback_aper_order;
 extern int fallback_aper_force;