x86/HVM: support IOMMU-related Viridian CPUID bits

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -50,6 +50,8 @@
 #define CPUID6A_APIC_OVERLAY    (1 << 0)
 #define CPUID6A_MSR_BITMAPS     (1 << 1)
 #define CPUID6A_NESTED_PAGING   (1 << 3)
+#define CPUID6A_DMA_REMAP       (1 << 4)
+#define CPUID6A_INTR_REMAP      (1 << 5)
 
 int cpuid_viridian_leaves(unsigned int leaf, unsigned int *eax,
                           unsigned int *ebx, unsigned int *ecx,
@@ -111,6 +113,12 @@ int cpuid_viridian_leaves(unsigned int l
             *eax |= CPUID6A_MSR_BITMAPS;
         if ( hap_enabled(d) )
             *eax |= CPUID6A_NESTED_PAGING;
+        if ( iommu_enabled )
+        {
+            *eax |= CPUID6A_DMA_REMAP;
+            if ( iommu_intremap )
+                *eax |= CPUID6A_INTR_REMAP;
+        }
         break;
     }