intel-iommu: Check for 'DMAR at zero' BIOS error earlier.

Chris Wright has some patches which let us fall back to swiotlb nicely
if IOMMU initialisation fails. But those are a bit much for 2.6.32.

Instead, let's shift the check for the biggest problem, the HP and Acer
BIOS bug which reports a DMAR at physical address zero. That one can
actually be checked much earlier -- before we even admit to having
detected an IOMMU in the first place. So the swiotlb init goes ahead as
we want.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 39 insertions, 10 deletions

diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index 22b02c6df854..e5f8fc164fd3 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -175,15 +175,6 @@ dmar_parse_one_drhd(struct acpi_dmar_header *header)
         int ret = 0;
 
         drhd = (struct acpi_dmar_hardware_unit *)header;
-        if (!drhd->address) {
-                /* Promote an attitude of violence to a BIOS engineer today */
-                WARN(1, "Your BIOS is broken; DMAR reported at address zero!\n"
-                     "BIOS vendor: %s; Ver: %s; Product Version: %s\n",
-                     dmi_get_system_info(DMI_BIOS_VENDOR),
-                     dmi_get_system_info(DMI_BIOS_VERSION),
-                     dmi_get_system_info(DMI_PRODUCT_VERSION));
-                return -ENODEV;
-        }
         dmaru = kzalloc(sizeof(*dmaru), GFP_KERNEL);
         if (!dmaru)
                 return -ENOMEM;
@@ -591,12 +582,50 @@ int __init dmar_table_init(void)
         return 0;
 }
 
+int __init check_zero_address(void)
+{
+        struct acpi_table_dmar *dmar;
+        struct acpi_dmar_header *entry_header;
+        struct acpi_dmar_hardware_unit *drhd;
+
+        dmar = (struct acpi_table_dmar *)dmar_tbl;
+        entry_header = (struct acpi_dmar_header *)(dmar + 1);
+
+        while (((unsigned long)entry_header) <
+                        (((unsigned long)dmar) + dmar_tbl->length)) {
+                /* Avoid looping forever on bad ACPI tables */
+                if (entry_header->length == 0) {
+                        printk(KERN_WARNING PREFIX
+                                "Invalid 0-length structure\n");
+                        return 0;
+                }
+
+                if (entry_header->type == ACPI_DMAR_TYPE_HARDWARE_UNIT) {
+                        drhd = (void *)entry_header;
+                        if (!drhd->address) {
+                                /* Promote an attitude of violence to a BIOS engineer today */
+                                WARN(1, "Your BIOS is broken; DMAR reported at address zero!\n"
+                                     "BIOS vendor: %s; Ver: %s; Product Version: %s\n",
+                                     dmi_get_system_info(DMI_BIOS_VENDOR),
+                                     dmi_get_system_info(DMI_BIOS_VERSION),
+                                     dmi_get_system_info(DMI_PRODUCT_VERSION));
+                                return 0;
+                        }
+                        break;
+                }
+
+                entry_header = ((void *)entry_header + entry_header->length);
+        }
+        return 1;
+}
+
 void __init detect_intel_iommu(void)
 {
         int ret;
 
         ret = dmar_table_detect();
-
+        if (ret)
+                ret = check_zero_address();
         {
 #ifdef CONFIG_INTR_REMAP
                 struct acpi_table_dmar *dmar;