hw/arm/virt: Reject gic-version=host for non-KVM

If you try to gic-version=host with TCG on a KVM aarch64 host,
qemu segfaults, since host requires KVM APIs.

Explicitly reject gic-version=host if KVM is not enabled

https://bugzilla.redhat.com/show_bug.cgi?id=1339977


Signed-off-by: Cole Robinson <crobinso@redhat.com>
Message-id: b1b3b0dd143b7995a7f4062966b80a2cf3e3c71e.1464273085.git.crobinso@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/virt.c

@@ -1122,10 +1122,14 @@ static void machvirt_init(MachineState *machine)
      * KVM is not available yet
      */
     if (!gic_version) {
+        if (!kvm_enabled()) {
+            error_report("gic-version=host requires KVM");
+            exit(1);
+        }
+
         gic_version = kvm_arm_vgic_probe();
         if (!gic_version) {
             error_report("Unable to determine GIC version supported by host");
-            error_printf("KVM acceleration is probably not supported\n");
             exit(1);
         }
     }