# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1233748806 0
# Node ID 6058887e55d7096f8b32c1f0576c601b080dc879
# Parent  7e15ccb7bbd88e550ada6a6b86196cc4e5d880b6
vtd: Add a boot parameter option for snoop control capability for VT-d.
The default is to use snoop control.

Signed-off-by: Xin, Xiaohui <xiaohui.xin@intel.com>

Index: xen-3.3.1-testing/xen/drivers/passthrough/iommu.c
===================================================================
--- xen-3.3.1-testing.orig/xen/drivers/passthrough/iommu.c
+++ xen-3.3.1-testing/xen/drivers/passthrough/iommu.c
@@ -34,6 +34,8 @@ int amd_iov_detect(void);
  *   no-pv                      Disable IOMMU for PV domains (default)
  *   force|required             Don't boot unless IOMMU is enabled
  *   passthrough                Bypass VT-d translation for Dom0
+ *   snoop                      Utilize the snoop control for IOMMU (default)
+ *   no-snoop                   Dont utilize the snoop control for IOMMU
  */
 custom_param("iommu", parse_iommu_param);
 int iommu_enabled = 0;
@@ -46,6 +48,7 @@ static void __init parse_iommu_param(cha
 {
     char *ss;
     iommu_enabled = 1;
+    iommu_snoop = 1;
 
     do {
         ss = strchr(s, ',');
@@ -63,6 +66,10 @@ static void __init parse_iommu_param(cha
             force_iommu = 1;
         else if ( !strcmp(s, "passthrough") )
             iommu_passthrough = 1;
+        else if ( !strcmp(s, "snoop") )
+            iommu_snoop = 1;
+        else if ( !strcmp(s, "no-snoop") )
+            iommu_snoop = 0;
 
         s = ss + 1;
     } while ( ss );
Index: xen-3.3.1-testing/xen/drivers/passthrough/vtd/dmar.c
===================================================================
--- xen-3.3.1-testing.orig/xen/drivers/passthrough/vtd/dmar.c
+++ xen-3.3.1-testing/xen/drivers/passthrough/vtd/dmar.c
@@ -530,13 +530,15 @@ int acpi_dmar_init(void)
     /* Giving that all devices within guest use same io page table,
      * enable snoop control only if all VT-d engines support it.
      */
-    iommu_snoop = 1;
-    for_each_drhd_unit ( drhd )
+    if ( iommu_snoop )
     {
-        iommu = drhd->iommu;
-        if ( !ecap_snp_ctl(iommu->ecap) ) {
-            iommu_snoop = 0;
-            break;
+        for_each_drhd_unit ( drhd )
+        {
+            iommu = drhd->iommu;
+            if ( !ecap_snp_ctl(iommu->ecap) ) {
+                iommu_snoop = 0;
+                break;
+            }
         }
     }