KVM: arm64: Enforce dependency on an ARMv8.4-aware toolchain

With the NV support of TLBI-range operations, KVM makes use of
instructions that are only supported by binutils versions >= 2.30.

This breaks the build for very old toolchains.

Make KVM support conditional on having ARMv8.4 support in the
assembler, side-stepping the issue.

Fixes: 5d476ca ("KVM: arm64: nv: Add handling of range-based TLBI operations")
Reported-by: Viresh Kumar <[email protected]>
Suggested-by: Arnd Bergmann <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Acked-by: Arnd Bergmann <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Oliver Upton <[email protected]>

Author: Marc Zyngier

arch/arm64/kvm/Kconfig

@@ -19,6 +19,7 @@ if VIRTUALIZATION
 
 menuconfig KVM
 	bool "Kernel-based Virtual Machine (KVM) support"
+	depends on AS_HAS_ARMV8_4
 	select KVM_COMMON
 	select KVM_GENERIC_HARDWARE_ENABLING
 	select KVM_GENERIC_MMU_NOTIFIER