Re: [Xen-devel] [PATCH] [VTD] Add 'force_iommu' option

[Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx>]

[Weidong Han]
> For security reasons, add 'force_iommu' option to ensure that it should
> not be possible under any conditions to boot Xen w/o VT-d being enabled.
> This would only be specified by users that really want the added
> security.

Here's a followup which collects all the iommu parameters into a
single parameter.  Makes things more intuitive from a users
perspective.

        eSk


---
iommu: Make the iommu boot parameters more generic and flexible

Make the 'iommu' boot parameter take a comma separated value indicating
wheter iommu is required to boot and whether to enable iommu for pv
domains.

Signed-off-by: Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx>


diff -r 152ba12fc55c xen/drivers/passthrough/iommu.c
--- a/xen/drivers/passthrough/iommu.c   Wed Aug 06 13:07:34 2008 +0100
+++ b/xen/drivers/passthrough/iommu.c   Wed Aug 06 13:55:46 2008 +0100
@@ -20,18 +20,48 @@
 
 extern struct iommu_ops intel_iommu_ops;
 extern struct iommu_ops amd_iommu_ops;
+static void parse_iommu_param(char *s);
 static int iommu_populate_page_table(struct domain *d);
 int intel_vtd_setup(void);
 int amd_iov_detect(void);
 
+/*
+ * The 'iommu' parameter enables the IOMMU.  Optional comma separated
+ * value may contain:
+ *
+ *   off|no|false|disable       Disable IOMMU (default)
+ *   pv                         Enable IOMMU for PV domains
+ *   no-pv                      Disable IOMMU for PV domains (default)
+ *   force|required             Don't boot unless IOMMU is enabled
+ */
+custom_param("iommu", parse_iommu_param);
 int iommu_enabled = 0;
-boolean_param("iommu", iommu_enabled);
+int iommu_pv_enabled = 0;
+int force_iommu = 0;
 
-int iommu_pv_enabled = 0;
-boolean_param("iommu_pv", iommu_pv_enabled);
+static void __init parse_iommu_param(char *s)
+{
+    char *ss;
+    iommu_enabled = 1;
 
-int force_iommu = 0;
-boolean_param("force_iommu", force_iommu);
+    do {
+        ss = strchr(s, ',');
+        if ( ss )
+            *ss = '\0';
+
+        if ( !strcmp(s, "off") || !strcmp(s, "no") || !strcmp(s, "false") ||
+             !strcmp(s, "0") || !strcmp(s, "disable") )
+            iommu_enabled = 0;
+        else if ( !strcmp(s, "pv") )
+            iommu_pv_enabled = 1;
+        else if ( !strcmp(s, "no-pv") )
+            iommu_pv_enabled = 0;
+        else if ( !strcmp(s, "force") || !strcmp(s, "required") )
+            force_iommu = 1;
+
+        s = ss + 1;
+    } while ( ss );
+}
 
 int iommu_domain_init(struct domain *domain)
 {

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