target-arm: Add CPU property to disable AArch64

Adds registration and get/set functions for enabling/disabling the AArch64
execution state on AArch64 CPUs.  By default AArch64 execution state is enabled
on AArch64 CPUs, setting the property to off, will disable the execution state.
The below QEMU invocation would have AArch64 execution state disabled.

    $ ./qemu-system-aarch64 -machine virt -cpu cortex-a57,aarch64=off

Also adds stripping of features from CPU model string in acquiring the ARM CPU
by name.

Signed-off-by: Greg Bellows <greg.bellows@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1423736974-14254-2-git-send-email-greg.bellows@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/target-arm/cpu64.c b/target-arm/cpu64.c
index bb778b3d92..823c739f08 100644
--- a/target-arm/cpu64.c
+++ b/target-arm/cpu64.c
@@ -32,6 +32,11 @@ static inline void set_feature(CPUARMState *env, int feature)
     env->features |= 1ULL << feature;
 }
 
+static inline void unset_feature(CPUARMState *env, int feature)
+{
+    env->features &= ~(1ULL << feature);
+}
+
 #ifndef CONFIG_USER_ONLY
 static uint64_t a57_l2ctlr_read(CPUARMState *env, const ARMCPRegInfo *ri)
 {
@@ -170,8 +175,42 @@ static const ARMCPUInfo aarch64_cpus[] = {
     { .name = NULL }
 };
 
+static bool aarch64_cpu_get_aarch64(Object *obj, Error **errp)
+{
+    ARMCPU *cpu = ARM_CPU(obj);
+
+    return arm_feature(&cpu->env, ARM_FEATURE_AARCH64);
+}
+
+static void aarch64_cpu_set_aarch64(Object *obj, bool value, Error **errp)
+{
+    ARMCPU *cpu = ARM_CPU(obj);
+
+    /* At this time, this property is only allowed if KVM is enabled.  This
+     * restriction allows us to avoid fixing up functionality that assumes a
+     * uniform execution state like do_interrupt.
+     */
+    if (!kvm_enabled()) {
+        error_setg(errp, "'aarch64' feature cannot be disabled "
+                         "unless KVM is enabled");
+        return;
+    }
+
+    if (value == false) {
+        unset_feature(&cpu->env, ARM_FEATURE_AARCH64);
+    } else {
+        set_feature(&cpu->env, ARM_FEATURE_AARCH64);
+    }
+}
+
 static void aarch64_cpu_initfn(Object *obj)
 {
+    object_property_add_bool(obj, "aarch64", aarch64_cpu_get_aarch64,
+                             aarch64_cpu_set_aarch64, NULL);
+    object_property_set_description(obj, "aarch64",
+                                    "Set on/off to enable/disable aarch64 "
+                                    "execution state ",
+                                    NULL);
 }
 
 static void aarch64_cpu_finalizefn(Object *obj)