target/arm: add "cortex-m0" CPU model

Define a "cortex-m0" ARMv6-M CPU model.

Most of the register reset values set by other CPU models are not
relevant for the cut-down ARMv6-M architecture.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180814162739.11814-3-stefanha@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu.c

@@ -1255,6 +1255,15 @@ static void arm11mpcore_initfn(Object *obj)
     cpu->reset_auxcr = 1;
 }
 
+static void cortex_m0_initfn(Object *obj)
+{
+    ARMCPU *cpu = ARM_CPU(obj);
+    set_feature(&cpu->env, ARM_FEATURE_V6);
+    set_feature(&cpu->env, ARM_FEATURE_M);
+
+    cpu->midr = 0x410cc200;
+}
+
 static void cortex_m3_initfn(Object *obj)
 {
     ARMCPU *cpu = ARM_CPU(obj);
@@ -1845,6 +1854,8 @@ static const ARMCPUInfo arm_cpus[] = {
     { .name = "arm1136",     .initfn = arm1136_initfn },
     { .name = "arm1176",     .initfn = arm1176_initfn },
     { .name = "arm11mpcore", .initfn = arm11mpcore_initfn },
+    { .name = "cortex-m0",   .initfn = cortex_m0_initfn,
+                             .class_init = arm_v7m_class_init },
     { .name = "cortex-m3",   .initfn = cortex_m3_initfn,
                              .class_init = arm_v7m_class_init },
     { .name = "cortex-m4",   .initfn = cortex_m4_initfn,