KVM: arm64: Stub EXPORT_SYMBOL for nVHE EL2 code

In order to ensure the module loader does not get confused if a symbol
is exported in EL2 nVHE code (as will be the case when we will compile
e.g. lib/memset.S into the EL2 object), make sure to stub all exports
using __DISABLE_EXPORTS in the nvhe folder.
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210203141931.615898-3-qperret@google.com

arch/arm64/kvm/hyp/nvhe/Makefile

@@ -3,8 +3,8 @@
 # Makefile for Kernel-based Virtual Machine module, HYP/nVHE part
 #
 
-asflags-y := -D__KVM_NVHE_HYPERVISOR__
-ccflags-y := -D__KVM_NVHE_HYPERVISOR__
+asflags-y := -D__KVM_NVHE_HYPERVISOR__ -D__DISABLE_EXPORTS
+ccflags-y := -D__KVM_NVHE_HYPERVISOR__ -D__DISABLE_EXPORTS
 
 obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
 	 hyp-main.o hyp-smp.o psci-relay.o