intel-iommu: Restore DMAR_BROKEN_GFX_WA option for broken graphics drivers

We need to give people a little more time to fix the broken drivers.
Re-introduce this, but tied in properly with the 'iommu=pt' support this
time. Change the config option name and make it default to 'no' too.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

arch/x86/Kconfig

@@ -1913,6 +1913,18 @@ config DMAR_DEFAULT_ON
 	  recommended you say N here while the DMAR code remains
 	  experimental.
 
+config DMAR_BROKEN_GFX_WA
+	def_bool n
+	prompt "Workaround broken graphics drivers (going away soon)"
+	depends on DMAR
+	---help---
+	  Current Graphics drivers tend to use physical address
+	  for DMA and avoid using DMA APIs. Setting this config
+	  option permits the IOMMU driver to set a unity map for
+	  all the OS-visible memory. Hence the driver can continue
+	  to use physical addresses for DMA, at least until this
+	  option is removed in the 2.6.32 kernel.
+
 config DMAR_FLOPPY_WA
 	def_bool y
 	depends on DMAR

drivers/pci/intel-iommu.c

@@ -2127,6 +2127,7 @@ static int iommu_prepare_static_identity_mapping(void)
 		return -EFAULT;
 
 	for_each_pci_dev(pdev) {
+		if (iommu_identity_mapping == 1 || IS_GFX_DEVICE(pdev)) {
 			printk(KERN_INFO "IOMMU: identity mapping for device %s\n",
 			       pci_name(pdev));
 
@@ -2138,6 +2139,7 @@ static int iommu_prepare_static_identity_mapping(void)
 			if (ret)
 				return ret;
 		}
+	}
 
 	return 0;
 }
@@ -2291,6 +2293,10 @@ int __init init_dmars(void)
 	 * identity mapping if iommu_identity_mapping is set.
 	 */
 	if (!iommu_pass_through) {
+#ifdef CONFIG_DMAR_BROKEN_GFX_WA
+		if (!iommu_identity_mapping)
+			iommu_identity_mapping = 2;
+#endif
 		if (iommu_identity_mapping)
 			iommu_prepare_static_identity_mapping();
 		/*
@@ -2444,6 +2450,9 @@ static int iommu_dummy(struct pci_dev *pdev)
 
 static int iommu_should_identity_map(struct pci_dev *pdev)
 {
+	if (iommu_identity_mapping == 2)
+		return IS_GFX_DEVICE(pdev);
+	else
 		return pdev->dma_mask > DMA_BIT_MASK(32);
 }