VT-d: prevent dom0 to use VT-d HW

pv-ops dom0 contains Linux upstream VT-d driver, and will go to enable
it when VT-d is set in kernel config file. It should not enable VT-d
in dom0.

Currently it already zaps ACPI DMAR signature to prevents dom0 using
VT-d HW when VT-d is enabled for Xen. But when VT-d is not enabled for
Xen, and VT-d is set in pv-ops kernel config file, pv-ops dom0 will go
to enable it. This will results in pv-ops dom0 booting failure. This
patch prevents dom0 to use VT-d HW whether VT-d is enabled or disabled
for Xen.

Signed-off-by: Weidong Han <weidong.han@intel.com>

diff --git a/xen/drivers/passthrough/vtd/dmar.c b/xen/drivers/passthrough/vtd/dmar.c
index 4386149ac9b91d2c3eb3246f8dfcff1267634fb0..7f8dbb72fb3f5dfeed37d1c3cc3be5fc73d4f2c0 100644 (file)
--- a/xen/drivers/passthrough/vtd/dmar.c
+++ b/xen/drivers/passthrough/vtd/dmar.c
@@ -517,6 +517,12 @@ static int __init acpi_parse_dmar(struct acpi_table_header *table)
 
     dmar = (struct acpi_table_dmar *)table;
 
+    if ( !iommu_enabled )
+    {
+        ret = -EINVAL;
+        goto out;
+    }
+
     if ( !dmar->width )
     {
         dprintk(XENLOG_WARNING VTDPREFIX, "Zero: Invalid DMAR width\n");
@@ -563,9 +569,6 @@ static int __init acpi_parse_dmar(struct acpi_table_header *table)
         entry_header = ((void *)entry_header + entry_header->length);
     }
 
-    /* Zap APCI DMAR signature to prevent dom0 using vt-d HW. */
-    dmar->header.signature[0] = '\0';
-
     if ( ret )
     {
         if ( force_iommu )
@@ -579,6 +582,9 @@ static int __init acpi_parse_dmar(struct acpi_table_header *table)
         }
     }
 
+out:
+    /* Zap ACPI DMAR signature to prevent dom0 using vt-d HW. */
+    dmar->header.signature[0] = '\0';
     return ret;
 }
 
@@ -599,9 +605,6 @@ int acpi_dmar_init(void)
     if ( force_iommu )
         iommu_enabled = 1;
 
-    if ( !iommu_enabled )
-        goto fail;
-
     rc = parse_dmar_table(acpi_parse_dmar);
     if ( rc )
         goto fail;