1 files changed, 29 insertions, 5 deletions

diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index 525a32487abd..56883fc1c7be 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -632,6 +632,9 @@ int __init check_zero_address(void)
                 }
 
                 if (entry_header->type == ACPI_DMAR_TYPE_HARDWARE_UNIT) {
+                        void __iomem *addr;
+                        u64 cap, ecap;
+
                         drhd = (void *)entry_header;
                         if (!drhd->address) {
                                 /* Promote an attitude of violence to a BIOS engineer today */
@@ -640,17 +643,38 @@ int __init check_zero_address(void)
                                      dmi_get_system_info(DMI_BIOS_VENDOR),
                                      dmi_get_system_info(DMI_BIOS_VERSION),
                                      dmi_get_system_info(DMI_PRODUCT_VERSION));
-#ifdef CONFIG_DMAR
-                                dmar_disabled = 1;
-#endif
-                                return 0;
+                                goto failed;
+                        }
+
+                        addr = early_ioremap(drhd->address, VTD_PAGE_SIZE);
+                        if (!addr ) {
+                                printk("IOMMU: can't validate: %llx\n", drhd->address);
+                                goto failed;
+                        }
+                        cap = dmar_readq(addr + DMAR_CAP_REG);
+                        ecap = dmar_readq(addr + DMAR_ECAP_REG);
+                        early_iounmap(addr, VTD_PAGE_SIZE);
+                        if (cap == (uint64_t)-1 && ecap == (uint64_t)-1) {
+                                /* Promote an attitude of violence to a BIOS engineer today */
+                                WARN(1, "Your BIOS is broken; DMAR reported at address %llx returns all ones!\n"
+                                     "BIOS vendor: %s; Ver: %s; Product Version: %s\n",
+                                      drhd->address,
+                                      dmi_get_system_info(DMI_BIOS_VENDOR),
+                                      dmi_get_system_info(DMI_BIOS_VERSION),
+                                      dmi_get_system_info(DMI_PRODUCT_VERSION));
+                                goto failed;
                         }
-                        break;
                 }
 
                 entry_header = ((void *)entry_header + entry_header->length);
         }
         return 1;
+
+failed:
+#ifdef CONFIG_DMAR
+        dmar_disabled = 1;
+#endif
+        return 0;
 }
 
 void __init detect_intel_iommu(void)