x86/traps: Don't call hvm_hypervisor_cpuid_leaf() for PV guests

Luckily, hvm_hypervisor_cpuid_leaf() and vmx_hypervisor_cpuid_leaf() are safe
to execute in the context of a PV guest, but HVM-specific feature flags
shouldn't be visible to PV guests.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>

xen/arch/x86/traps.c

@@ -928,6 +928,11 @@ int cpuid_hypervisor_leaves( uint32_t idx, uint32_t sub_idx,
         break;
 
     case 4:
+        if ( !has_hvm_container_domain(currd) )
+        {
+            *eax = *ebx = *ecx = *edx = 0;
+            break;
+        }
         hvm_hypervisor_cpuid_leaf(sub_idx, eax, ebx, ecx, edx);
         break;