Revert 26503:69398345c10e

This conflicts with changes done in 26486:7648ef657fe7 and
26489:83a3fa9c8434 (i.e. the code added by them needs adjustment in
order for the change here to be correct).

xen/arch/x86/hvm/hvm.c

@@ -3900,25 +3900,20 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
                     rc = -EPERM;
                     break;
                 }
-                if ( !a.value )
-                    break;
                 if ( a.value > 1 )
                     rc = -EINVAL;
+                if ( !is_hvm_domain(d) )
+                    rc = -EINVAL;
                 /* Remove the check below once we have
                  * shadow-on-shadow.
                  */
-                if ( cpu_has_svm && !paging_mode_hap(d) )
+                if ( cpu_has_svm && !paging_mode_hap(d) && a.value )
                     rc = -EINVAL;
                 /* Set up NHVM state for any vcpus that are already up */
                 if ( !d->arch.hvm_domain.params[HVM_PARAM_NESTEDHVM] )
-                {
                     for_each_vcpu(d, v)
                         if ( rc == 0 )
                             rc = nestedhvm_vcpu_initialise(v);
-                    if ( rc )
-                        for_each_vcpu(d, v)
-                            nestedhvm_vcpu_destroy(v);
-                }
                 break;
             case HVM_PARAM_BUFIOREQ_EVTCHN:
                 rc = -EINVAL;

xen/arch/x86/hvm/nestedhvm.c

@@ -87,7 +87,7 @@ nestedhvm_vcpu_initialise(struct vcpu *v)
 void
 nestedhvm_vcpu_destroy(struct vcpu *v)
 {
-    if ( hvm_funcs.nhvm_vcpu_destroy )
+    if ( nestedhvm_enabled(v->domain) && hvm_funcs.nhvm_vcpu_destroy )
         hvm_funcs.nhvm_vcpu_destroy(v);
 }