KVM: arm64: selftests: Alias EL1 registers to EL2 counterparts

FEAT_VHE has the somewhat nice property of implicitly redirecting EL1
register aliases to their corresponding EL2 representations when E2H=1.
Unfortunately, there's no such abstraction for userspace and EL2
registers are always accessed by their canonical encoding.

Introduce a helper that applies EL2 redirections to sysregs and use
aggressive inlining to catch misuse at compile time. Go a little past
the architectural definition for ease of use for test authors (e.g. the
stack pointer).

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>

tools/testing/selftests/kvm/include/kvm_util.h

@@ -63,6 +63,9 @@ struct kvm_vcpu {
 	struct kvm_run *run;
 #ifdef __x86_64__
 	struct kvm_cpuid2 *cpuid;
+#endif
+#ifdef __aarch64__
+	struct kvm_vcpu_init init;
 #endif
 	struct kvm_binary_stats stats;
 	struct kvm_dirty_gfn *dirty_gfns;