[PATCH] x86/CPUID: suppress IOMMU related hypervisor leaf data

[Jan Beulich <jbeulich@xxxxxxxx>]

Now that the IOMMU for guests can't be enabled "on demand" anymore,
there's also no reason to expose the related CPUID bit "just in case".

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

--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1050,7 +1050,8 @@ void cpuid_hypervisor_leaves(const struc
          * Indicate that memory mapped from other domains (either grants or
          * foreign pages) has valid IOMMU entries.
          */
-        res->a |= XEN_HVM_CPUID_IOMMU_MAPPINGS;
+        if ( is_iommu_enabled(d) )
+            res->a |= XEN_HVM_CPUID_IOMMU_MAPPINGS;
 
         /* Indicate presence of vcpu id and set it in ebx */
         res->a |= XEN_HVM_CPUID_VCPU_ID_PRESENT;