KVM: arm64: Restructure check for SVE support in FP trap handler

We share the same handler for general floating point and SVE traps with a
check to make sure we don't handle any SVE traps if the system doesn't
have SVE support. Since we will be adding SME support and wishing to handle
that along with other FP related traps rewrite the check to be more scalable
and a bit clearer too, ensuring we don't misidentify SME traps as SVE ones.
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221214-kvm-arm64-sme-context-switch-v2-2-57ba0082e9ff@kernel.org

arch/arm64/kvm/hyp/include/hyp/switch.h

@@ -176,9 +176,17 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
 	sve_guest = vcpu_has_sve(vcpu);
 	esr_ec = kvm_vcpu_trap_get_class(vcpu);
 
-	/* Don't handle SVE traps for non-SVE vcpus here: */
-	if (!sve_guest && esr_ec != ESR_ELx_EC_FP_ASIMD)
+	/* Only handle traps the vCPU can support here: */
+	switch (esr_ec) {
+	case ESR_ELx_EC_FP_ASIMD:
+		break;
+	case ESR_ELx_EC_SVE:
+		if (!sve_guest)
+			return false;
+		break;
+	default:
 		return false;
+	}
 
 	/* Valid trap.  Switch the context: */