IOMMU: Fail if intremap is not available and iommu=required/force.

Rather than sprinkling panic()s throughout the setup code hoist the
check up into common code.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Keir Fraser <keir@xen.org>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
xen-unstable changeset:   23402:f979a1a69fe3
xen-unstable date:        Thu May 26 08:18:44 2011 +0100

xen/drivers/passthrough/iommu.c

@@ -309,6 +309,7 @@ int deassign_device(struct domain *d, u8 bus, u8 devfn)
 int __init iommu_setup(void)
 {
     int rc = -ENODEV;
+    bool_t force_intremap = force_iommu && iommu_intremap;
 
     if ( iommu_dom0_strict )
         iommu_passthrough = 0;
@@ -319,8 +320,10 @@ int __init iommu_setup(void)
         iommu_enabled = (rc == 0);
     }
 
-    if ( force_iommu && !iommu_enabled )
-        panic("IOMMU setup failed, crash Xen for security purpose!\n");
+    if ( (force_iommu && !iommu_enabled) ||
+         (force_intremap && !iommu_intremap) )
+        panic("Couldn't enable %s and iommu=required/force\n",
+              !iommu_enabled ? "IOMMU" : "Interrupt Remapping");
 
     if ( !iommu_enabled )
     {

xen/drivers/passthrough/vtd/iommu.c

@@ -1996,6 +1996,7 @@ static int init_vtd_hw(void)
             iommu = drhd->iommu;
             if ( enable_intremap(iommu, 0) != 0 )
             {
+                iommu_intremap = 0;
                 dprintk(XENLOG_WARNING VTDPREFIX,
                         "Failed to enable Interrupt Remapping!\n");
                 break;