target/arm/kvm: gic: Prevent creating userspace GICv3 with KVM

KVM doesn't support emulating a GICv3 in userspace, only GICv2.  We
currently attempt this anyway, and as a result a KVM guest doesn't
receive interrupts and the user is left wondering why.  Report an error
to the user if this particular combination is requested.
Signed-off-by: NChristoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180201205307.30343-1-christoffer.dall@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/kvm_arm.h

@@ -234,6 +234,10 @@ static inline const char *gicv3_class_name(void)
         exit(1);
 #endif
     } else {
+        if (kvm_enabled()) {
+            error_report("Userspace GICv3 is not supported with KVM");
+            exit(1);
+        }
         return "arm-gicv3";
     }
 }