diff --git a/repos/base-foc/src/lib/base/x86/vm_session.cc b/repos/base-foc/src/lib/base/x86/vm_session.cc
index 9e49f1f4f2..769c12866d 100644
--- a/repos/base-foc/src/lib/base/x86/vm_session.cc
+++ b/repos/base-foc/src/lib/base/x86/vm_session.cc
@@ -152,6 +152,7 @@ struct Vcpu : Thread
 
 			MSR_FMASK  = 0x2842,
 			MSR_LSTAR  = 0x2844,
+			MSR_CSTAR  = 0x2846,
 			MSR_STAR   = 0x284a,
 
 			KERNEL_GS_BASE = 0x284c,
@@ -614,6 +615,7 @@ struct Vcpu : Thread
 
 			state.star.value(l4_vm_vmx_read(vmcs, Vmcs::MSR_STAR));
 			state.lstar.value(l4_vm_vmx_read(vmcs, Vmcs::MSR_LSTAR));
+			state.cstar.value(l4_vm_vmx_read(vmcs, Vmcs::MSR_CSTAR));
 			state.fmask.value(l4_vm_vmx_read(vmcs, Vmcs::MSR_FMASK));
 			state.kernel_gs_base.value(l4_vm_vmx_read(vmcs, Vmcs::KERNEL_GS_BASE));
 
@@ -756,7 +758,7 @@ struct Vcpu : Thread
 				error("pdpte not implemented");
 			}
 
-			if (state.star.valid() || state.lstar.valid() ||
+			if (state.star.valid() || state.lstar.valid() || state.cstar.valid() ||
 			    state.fmask.valid() || state.kernel_gs_base.valid()) {
 
 				error("star, fstar, fmask, kernel_gs_base not implemented");
@@ -813,6 +815,9 @@ struct Vcpu : Thread
 			if (state.lstar.valid())
 				l4_vm_vmx_write(vmcs, Vmcs::MSR_LSTAR, state.lstar.value());
 
+			if (state.cstar.valid())
+				l4_vm_vmx_write(vmcs, Vmcs::MSR_CSTAR, state.cstar.value());
+
 			if (state.fmask.valid())
 				l4_vm_vmx_write(vmcs, Vmcs::MSR_FMASK, state.fmask.value());
 
@@ -1032,7 +1037,7 @@ struct Vcpu : Thread
 				vmcb->control_area.tsc_offset = _tsc_offset;
 			}
 
-			if (state.star.value() || state.lstar.value() ||
+			if (state.star.value() || state.lstar.value() || state.cstar.value() ||
 			    state.fmask.value() || state.kernel_gs_base.value())
 				error(__LINE__, " not implemented");
 
diff --git a/repos/base-nova/include/nova/syscall-generic.h b/repos/base-nova/include/nova/syscall-generic.h
index 802c12d090..ac0ea8b8cd 100644
--- a/repos/base-nova/include/nova/syscall-generic.h
+++ b/repos/base-nova/include/nova/syscall-generic.h
@@ -566,6 +566,7 @@ namespace Nova {
 				mword_t cr8, efer;
 				unsigned long long star;
 				unsigned long long lstar;
+				unsigned long long cstar;
 				unsigned long long fmask;
 				unsigned long long kernel_gs_base;
 				unsigned tpr;
@@ -625,6 +626,8 @@ namespace Nova {
 		inline void write_star(mword_t value) { star = value; }
 		inline mword_t read_lstar() { return lstar; }
 		inline void write_lstar(mword_t value) { lstar = value; }
+		inline mword_t read_cstar() { return cstar; }
+		inline void write_cstar(mword_t value) { cstar = value; }
 		inline mword_t read_fmask() { return fmask; }
 		inline void write_fmask(mword_t value) { fmask = value; }
 		inline mword_t read_kernel_gs_base() { return kernel_gs_base; }
@@ -656,6 +659,8 @@ namespace Nova {
 		inline void write_star(mword_t) { }
 		inline mword_t read_lstar() { return 0UL; }
 		inline void write_lstar(mword_t) { }
+		inline mword_t read_cstar() { return 0UL; }
+		inline void write_cstar(mword_t) { }
 		inline mword_t read_fmask() { return 0UL; }
 		inline void write_fmask(mword_t) { }
 		inline mword_t read_kernel_gs_base() { return 0UL; }
diff --git a/repos/base-nova/ports/nova.hash b/repos/base-nova/ports/nova.hash
index e3069ac1e2..fce983590c 100644
--- a/repos/base-nova/ports/nova.hash
+++ b/repos/base-nova/ports/nova.hash
@@ -1 +1 @@
-e0a4960688b5e6aac8f77998dda98e891e19441c
+c9523ea8553360b7d9732280817bb2ba1ef701de
diff --git a/repos/base-nova/ports/nova.port b/repos/base-nova/ports/nova.port
index b49e372139..5e2500dd6a 100644
--- a/repos/base-nova/ports/nova.port
+++ b/repos/base-nova/ports/nova.port
@@ -4,7 +4,7 @@ DOWNLOADS := nova.git
 
 # r10 branch
 URL(nova) := https://github.com/alex-ab/NOVA.git
-REV(nova) := af931a15fc6b032615f076e946b6026a31dbacaf
+REV(nova) := 7f9d73e3266c7cb7418c18fb37bb97e3c6b2442d
 DIR(nova) := src/kernel/nova
 
 PATCHES   := $(sort $(wildcard $(REP_DIR)/patches/*.patch))
diff --git a/repos/base-nova/src/lib/base/vm_session.cc b/repos/base-nova/src/lib/base/vm_session.cc
index 20fd4c2073..d9031d175f 100644
--- a/repos/base-nova/src/lib/base/vm_session.cc
+++ b/repos/base-nova/src/lib/base/vm_session.cc
@@ -191,6 +191,7 @@ struct Vcpu {
 			if (utcb.mtd & Nova::Mtd::SYSCALL_SWAPGS) {
 				state.star.value(utcb.read_star());
 				state.lstar.value(utcb.read_lstar());
+				state.cstar.value(utcb.read_cstar());
 				state.fmask.value(utcb.read_fmask());
 				state.kernel_gs_base.value(utcb.read_kernel_gs_base());
 			}
@@ -384,11 +385,13 @@ struct Vcpu {
 			}
 
 			if (state.star.valid() || state.lstar.valid() ||
-			    state.fmask.valid() || state.kernel_gs_base.valid()) {
+			    state.cstar.valid() || state.fmask.valid() ||
+			    state.kernel_gs_base.valid()) {
 
 				utcb.mtd  |= Nova::Mtd::SYSCALL_SWAPGS;
 				utcb.write_star(state.star.value());
 				utcb.write_lstar(state.lstar.value());
+				utcb.write_cstar(state.cstar.value());
 				utcb.write_fmask(state.fmask.value());
 				utcb.write_kernel_gs_base(state.kernel_gs_base.value());
 			}
@@ -671,7 +674,8 @@ struct Vcpu {
 				mtd |= Nova::Mtd::PDPTE;
 
 			if (state.star.valid() || state.lstar.valid() ||
-			    state.fmask.valid() || state.kernel_gs_base.valid())
+			    state.cstar.valid() || state.fmask.valid() ||
+			    state.kernel_gs_base.valid())
 				mtd |= Nova::Mtd::SYSCALL_SWAPGS;
 
 			if (state.tpr.valid() || state.tpr_threshold.valid())
diff --git a/repos/base-sel4/src/lib/base/x86/vm_session.cc b/repos/base-sel4/src/lib/base/x86/vm_session.cc
index 1ec704145a..2a1f8ca265 100644
--- a/repos/base-sel4/src/lib/base/x86/vm_session.cc
+++ b/repos/base-sel4/src/lib/base/x86/vm_session.cc
@@ -374,12 +374,12 @@ struct Vcpu : Genode::Thread
 #endif
 			}
 
-			if (state.star.valid() || state.lstar.valid() ||
+			if (state.star.valid() || state.lstar.valid() || state.cstar.valid() ||
 			    state.fmask.valid() || state.kernel_gs_base.valid())
 			{
 				if (_show_error_unsupported_star) {
 					_show_error_unsupported_star = false;
-					Genode::error("star, lstar, fmask, gs_base not supported by seL4");
+					Genode::error("star, lstar, cstar, fmask, gs_base not supported by seL4");
 				}
 			}
 
@@ -704,7 +704,7 @@ struct Vcpu : Genode::Thread
 
 			state.efer.value(_read_vmcs(service, Vmcs::EFER));
 
-			/* XXX star, lstar, fmask, kernel_gs_base not supported by seL4 */
+			/* XXX star, lstar, cstar, fmask, kernel_gs_base not supported by seL4 */
 
 			/* XXX tpr and tpr_threshold not supported by seL4 */
 		}
diff --git a/repos/base/include/spec/x86/cpu/vm_state.h b/repos/base/include/spec/x86/cpu/vm_state.h
index 291120ad4b..67c7029905 100644
--- a/repos/base/include/spec/x86/cpu/vm_state.h
+++ b/repos/base/include/spec/x86/cpu/vm_state.h
@@ -134,6 +134,7 @@ struct Genode::Vm_state
 
 	Register<uint64_t> star;
 	Register<uint64_t> lstar;
+	Register<uint64_t> cstar;
 	Register<uint64_t> fmask;
 	Register<uint64_t> kernel_gs_base;
 
diff --git a/repos/ports/ports/seoul.hash b/repos/ports/ports/seoul.hash
index bc2a02cc44..d6a3fd120a 100644
--- a/repos/ports/ports/seoul.hash
+++ b/repos/ports/ports/seoul.hash
@@ -1 +1 @@
-e8d6968e967852affc6a7290936466f032dc210b
+e4c5e41a5d3b5398a310dbc39b52a5393526c816
diff --git a/repos/ports/ports/seoul.port b/repos/ports/ports/seoul.port
index df1daca58f..945118f92c 100644
--- a/repos/ports/ports/seoul.port
+++ b/repos/ports/ports/seoul.port
@@ -3,8 +3,8 @@ VERSION   := git
 DOWNLOADS := seoul.git
 
 URL(seoul) := https://github.com/alex-ab/seoul.git
-# branch genode_20_02
-REV(seoul) := bcbb781d9412fe8c10d6e324e02116faf04b8d1f
+# branch genode_20_11
+REV(seoul) := 9c009e7ad2b5ec9fbafdc731e8796f33ff90e921
 DIR(seoul) := src/app/seoul
 
 #
diff --git a/repos/ports/src/app/seoul/state.cc b/repos/ports/src/app/seoul/state.cc
index 17d4523aac..d06d856557 100644
--- a/repos/ports/src/app/seoul/state.cc
+++ b/repos/ports/src/app/seoul/state.cc
@@ -373,10 +373,10 @@ unsigned Seoul::read_vm_state(Genode::Vm_state &state, CpuState &seoul)
 		Genode::warning("pdpte not supported by Seoul");
 	}
 
-	if (state.star.valid() || state.lstar.valid() ||
+	if (state.star.valid() || state.lstar.valid() || state.cstar.valid() ||
 	    state.fmask.valid() || state.kernel_gs_base.valid()) {
 
-		Genode::warning("star, lstar, fmask, kernel_gs not supported by Seoul");
+		Genode::warning("star, lstar, cstar, fmask, kernel_gs not supported by Seoul");
 	}
 
 	if (state.tpr.valid() || state.tpr_threshold.valid()) {
diff --git a/repos/ports/src/virtualbox5/spec/nova/vcpu.h b/repos/ports/src/virtualbox5/spec/nova/vcpu.h
index e375e25425..e0951430e4 100644
--- a/repos/ports/src/virtualbox5/spec/nova/vcpu.h
+++ b/repos/ports/src/virtualbox5/spec/nova/vcpu.h
@@ -517,6 +517,7 @@ class Vcpu_handler : public Vmm::Vcpu_dispatcher<Genode::Thread>,
 			utcb->mtd |= Mtd::SYSCALL_SWAPGS;
 			utcb->write_star(pCtx->msrSTAR);
 			utcb->write_lstar(pCtx->msrLSTAR);
+			utcb->write_cstar(pCtx->msrCSTAR);
 			utcb->write_fmask(pCtx->msrSFMASK);
 			utcb->write_kernel_gs_base(pCtx->msrKERNELGSBASE);
 
@@ -604,6 +605,9 @@ class Vcpu_handler : public Vmm::Vcpu_dispatcher<Genode::Thread>,
 			if (pCtx->msrLSTAR != utcb->read_lstar())
 				CPUMSetGuestMsr(pVCpu, MSR_K8_LSTAR, utcb->read_lstar());
 
+			if (pCtx->msrCSTAR != utcb->read_cstar())
+				CPUMSetGuestMsr(pVCpu, MSR_K8_CSTAR, utcb->read_cstar());
+
 			if (pCtx->msrSFMASK != utcb->read_fmask())
 				CPUMSetGuestMsr(pVCpu, MSR_K8_SF_MASK, utcb->read_fmask());
 
diff --git a/repos/ports/src/virtualbox5/vcpu.h b/repos/ports/src/virtualbox5/vcpu.h
index 707774c271..e2d3d05b14 100644
--- a/repos/ports/src/virtualbox5/vcpu.h
+++ b/repos/ports/src/virtualbox5/vcpu.h
@@ -345,6 +345,7 @@ class Vcpu_handler : public Genode::List<Vcpu_handler>::Element
 
 			_state->star.value(pCtx->msrSTAR);
 			_state->lstar.value(pCtx->msrLSTAR);
+			_state->cstar.value(pCtx->msrCSTAR);
 			_state->fmask.value(pCtx->msrSFMASK);
 			_state->kernel_gs_base.value(pCtx->msrKERNELGSBASE);
 
@@ -437,6 +438,9 @@ class Vcpu_handler : public Genode::List<Vcpu_handler>::Element
 			if (pCtx->msrLSTAR != _state->lstar.value())
 				CPUMSetGuestMsr(pVCpu, MSR_K8_LSTAR, _state->lstar.value());
 
+			if (pCtx->msrCSTAR != _state->cstar.value())
+				CPUMSetGuestMsr(pVCpu, MSR_K8_CSTAR, _state->cstar.value());
+
 			if (pCtx->msrSFMASK != _state->fmask.value())
 				CPUMSetGuestMsr(pVCpu, MSR_K8_SF_MASK, _state->fmask.value());