diff --git a/repos/ports/src/virtualbox/nova/sup.cc b/repos/ports/src/virtualbox/nova/sup.cc
index a6875d8b0a..0cb5dd20dc 100644
--- a/repos/ports/src/virtualbox/nova/sup.cc
+++ b/repos/ports/src/virtualbox/nova/sup.cc
@@ -61,10 +61,14 @@ void SUPR3QueryHWACCLonGenodeSupport(VM * pVM)
 		pVM->hm.s.svm.fSupported = hip->has_feature_svm();
 		pVM->hm.s.vmx.fSupported = hip->has_feature_vmx();
 
-		PINF("support svm %u vmx %u", hip->has_feature_svm(), hip->has_feature_vmx());
-	} catch (...) {
-		PWRN("No hardware acceleration available - execution will be slow!");
-	} /* if we get an exception let hardware support off */
+		if (hip->has_feature_svm() || hip->has_feature_vmx()) {
+			PINF("Using %s virtualization extension.",
+			     hip->has_feature_svm() ? "SVM" : "VMX");
+			return;
+		}
+	} catch (...) { /* if we get an exception let hardware support off */ }
+
+	PWRN("No virtualization hardware acceleration available");
 }
 
 
@@ -116,7 +120,8 @@ int SUPR3CallVMMR0Ex(PVMR0 pVMR0, VMCPUID idCpu, unsigned
 		return VINF_SUCCESS;
 
 	case VMMR0_DO_GVMM_SCHED_POKE:
-		vcpu_handler->recall();
+		if (vcpu_handler)
+			vcpu_handler->recall();
 		return VINF_SUCCESS;
 
 	default:
diff --git a/repos/ports/src/virtualbox/thread.cc b/repos/ports/src/virtualbox/thread.cc
index 3d10f1f235..1803099dcf 100644
--- a/repos/ports/src/virtualbox/thread.cc
+++ b/repos/ports/src/virtualbox/thread.cc
@@ -5,7 +5,7 @@
  */
 
 /*
- * Copyright (C) 2014 Genode Labs GmbH
+ * Copyright (C) 2014-2015 Genode Labs GmbH
  *
  * This file is distributed under the terms of the GNU General Public License
  * version 2.
@@ -29,7 +29,7 @@
 /* vbox */
 #include <internal/thread.h>
 
-static Genode::Cpu_session * get_cpu_session(RTTHREADTYPE type) {
+static Genode::Cpu_connection * cpu_connection(RTTHREADTYPE type) {
 	using namespace Genode;
 
 	static Cpu_connection * con[RTTHREADTYPE_END - 1];
@@ -55,16 +55,12 @@ static Genode::Cpu_session * get_cpu_session(RTTHREADTYPE type) {
 
 	con[type - 1] = new (env()->heap()) Cpu_connection(data, prio);
 
-	/* upgrade memory of cpu session for frequent used thread type */
-	if (type == RTTHREADTYPE_IO)
-		Genode::env()->parent()->upgrade(con[type - 1]->cap(), "ram_quota=16384");
-
 	return con[type - 1];
 }
 
 
-extern "C" int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
-	                          void *(*start_routine) (void *), void *arg)
+static int create_thread(pthread_t *thread, const pthread_attr_t *attr,
+	                     void *(*start_routine) (void *), void *arg)
 {
 	PRTTHREADINT rtthread = reinterpret_cast<PRTTHREADINT>(arg);
 
@@ -85,22 +81,21 @@ extern "C" int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
 		Assert(rtthread->enmType == RTTHREADTYPE_EMULATION);
 
 	if (rtthread->enmType == RTTHREADTYPE_EMULATION) {
-		Genode::Cpu_session * cpu_session = get_cpu_session(RTTHREADTYPE_EMULATION);
-/*
-		Genode::Affinity::Space cpu_space = cpu_session->affinity_space();
-		Genode::Affinity::Location location = cpu_space.location_of_index(i);
-*/
+		Genode::Cpu_session * cpu_session = cpu_connection(RTTHREADTYPE_EMULATION);
 		Genode::Affinity::Location location;
 		if (create_emt_vcpu(thread, stack_size, attr, start_routine, arg,
 		                    cpu_session, location))
 			return 0;
-		/* no haredware support, create normal pthread thread */
+		/*
+		 * The virtualization layer had no need to setup the EMT
+		 * specially, so create it as a ordinary pthread.
+		 */
 	}
 
 	pthread_t thread_obj = new (Genode::env()->heap())
 	                           pthread(attr ? *attr : 0, start_routine,
 	                           arg, stack_size, rtthread->szName,
-	                           get_cpu_session(rtthread->enmType));
+	                           cpu_connection(rtthread->enmType));
 
 	if (!thread_obj)
 		return EAGAIN;
@@ -112,6 +107,31 @@ extern "C" int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
 	return 0;
 }
 
+extern "C" int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
+                              void *(*start_routine) (void *), void *arg)
+{
+	PRTTHREADINT rtthread = reinterpret_cast<PRTTHREADINT>(arg);
+
+	/* retry thread creation once after CPU session upgrade */
+	for (unsigned i = 0; i < 2; i++) {
+		using namespace Genode;
+
+		try {
+			return create_thread(thread, attr, start_routine, arg);
+		} catch (Cpu_session::Out_of_metadata) {
+			PWRN("Upgrading memory for creation of thread '%s'",
+			     rtthread->szName);
+			env()->parent()->upgrade(cpu_connection(rtthread->enmType)->cap(),
+			                         "ram_quota=4096");
+		} catch (...) { break; }
+	}
+
+	PERR("Could not create vbox pthread - halt");
+	Genode::Lock lock(Genode::Lock::LOCKED);
+	lock.lock();
+	return EAGAIN;
+}
+
 extern "C" int pthread_attr_setdetachstate(pthread_attr_t *, int)
 {
 	return 0;