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 Benn?e <redacted>

---
v2
  - convert to using HSR_EC
v3
  - use internals.h definitions
v10
  - fix arm32 build
  - remove redundent flag setting (done in main kvm.c)
  - more words on fail case
---
 target-arm/kvm64.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/target-arm/kvm64.c b/target-arm/kvm64.c
index 3b3929d..5f96cde 100644
--- a/target-arm/kvm64.c
+++ b/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;

-- 
2.6.3