thunderbolt: Use pre-boot DMA protection on AMD systems

The information is exported from the IOMMU driver whether or not
pre-boot DMA protection has been enabled on AMD systems.  Use this
information to properly set iomma_dma_protection.

Link: https://docs.microsoft.com/en-us/windows-hardware/design/device-experiences/oem-kernel-dma-protection
Link: https://www.amd.com/system/files/TechDocs/48882_IOMMU.pdf
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>

drivers/thunderbolt/domain.c

@@ -6,6 +6,7 @@
  * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
  */
 
+#include <linux/amd-iommu.h>
 #include <linux/device.h>
 #include <linux/dmar.h>
 #include <linux/idr.h>
@@ -259,11 +260,15 @@ static ssize_t iommu_dma_protection_show(struct device *dev,
 {
 	/*
 	 * Kernel DMA protection is a feature where Thunderbolt security is
-	 * handled natively using IOMMU. It is enabled when IOMMU is
-	 * enabled and ACPI DMAR table has DMAR_PLATFORM_OPT_IN set.
+	 * handled natively using IOMMU. It is enabled when the IOMMU is
+	 * enabled and either:
+	 * ACPI DMAR table has DMAR_PLATFORM_OPT_IN set
+	 * or
+	 * ACPI IVRS table has DMA_REMAP bitset
 	 */
 	return sprintf(buf, "%d\n",
-		       iommu_present(&pci_bus_type) && dmar_platform_optin());
+		       iommu_present(&pci_bus_type) &&
+		       (dmar_platform_optin() || amd_ivrs_remap_support()));
 }
 static DEVICE_ATTR_RO(iommu_dma_protection);