KVM: arm64: nv: Fold guest's HCR_EL2 configuration into the host's

When entering a L2 guest (nested virt enabled, but not in hypervisor
context), we need to honor the traps the L1 guest has asked enabled.

For now, just OR the guest's HCR_EL2 into the host's. We may have to do
some filtering in the future though.

Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/hyp/vhe/switch.c

@@ -80,6 +80,8 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
 			if (!vcpu_el2_tge_is_set(vcpu))
 				hcr |= HCR_AT | HCR_TTLB;
 		}
+	} else if (nested_virt_in_use(vcpu)) {
+		hcr |= __vcpu_sys_reg(vcpu, HCR_EL2);
 	}
 
 	___activate_traps(vcpu, hcr);