1 files changed, 12 insertions, 2 deletions

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index dee88c6cb3ef..4dfce3dad6ab 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -3761,14 +3761,24 @@ static void __devinit quirk_iommu_rwbf(struct pci_dev *dev)
 
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2a40, quirk_iommu_rwbf);
 
+#define GGC 0x52
+#define GGC_MEMORY_SIZE_MASK    (0xf << 8)
+#define GGC_MEMORY_SIZE_NONE    (0x0 << 8)
+#define GGC_MEMORY_SIZE_1M      (0x1 << 8)
+#define GGC_MEMORY_SIZE_2M      (0x3 << 8)
+#define GGC_MEMORY_VT_ENABLED   (0x8 << 8)
+#define GGC_MEMORY_SIZE_2M_VT   (0x9 << 8)
+#define GGC_MEMORY_SIZE_3M_VT   (0xa << 8)
+#define GGC_MEMORY_SIZE_4M_VT   (0xb << 8)
+
 static void __devinit quirk_calpella_no_shadow_gtt(struct pci_dev *dev)
 {
         unsigned short ggc;
 
-        if (pci_read_config_word(dev, 0x52, &ggc))
+        if (pci_read_config_word(dev, GGC, &ggc))
                 return;
 
-        if (!(ggc & 0x800)) {
+        if (!(ggc & GGC_MEMORY_VT_ENABLED)) {
                 printk(KERN_INFO "DMAR: BIOS has allocated no shadow GTT; disabling IOMMU for graphics\n");
                 dmar_map_gfx = 0;
         }