target-arm: kvm - support for single step

This adds support for single-step. There isn't much to do on the QEMU
side as after we set-up the request for single step via the debug ioctl
it is all handled within the kernel.

The actual setting of the KVM_GUESTDBG_SINGLESTEP flag is already in the
common code. If the kernel doesn't support guest debug the ioctl will
simply error.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1449599553-24713-4-git-send-email-alex.bennee@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target-arm/kvm64.c

@@ -534,6 +534,13 @@ bool kvm_arm_handle_debug(CPUState *cs, struct kvm_debug_exit_arch *debug_exit)
     kvm_cpu_synchronize_state(cs);
 
     switch (hsr_ec) {
+    case EC_SOFTWARESTEP:
+        if (cs->singlestep_enabled) {
+            return true;
+        } else {
+            error_report("Came out of SINGLE STEP when not enabled");
+        }
+        break;
     case EC_AA64_BKPT:
         if (kvm_find_sw_breakpoint(cs, env->pc)) {
             return true;