accel: Destroy HAX vCPU threads once done

When the vCPU thread finished its processing, destroy
it and signal its destruction to generic vCPU management
layer.

Add a sanity check for the vCPU accelerator context.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230624174121.11508-6-philmd@linaro.org>

target/i386/hax/hax-accel-ops.c

@@ -53,6 +53,8 @@ static void *hax_cpu_thread_fn(void *arg)
 
         qemu_wait_io_event(cpu);
     } while (!cpu->unplug || cpu_can_run(cpu));
+    hax_vcpu_destroy(cpu);
+    cpu_thread_signal_destroyed(cpu);
     rcu_unregister_thread();
     return NULL;
 }
@@ -69,6 +71,7 @@ static void hax_start_vcpu_thread(CPUState *cpu)
              cpu->cpu_index);
     qemu_thread_create(cpu->thread, thread_name, hax_cpu_thread_fn,
                        cpu, QEMU_THREAD_JOINABLE);
+    assert(cpu->hax_vcpu);
 #ifdef _WIN32
     cpu->hThread = qemu_thread_get_handle(cpu->thread);
 #endif

target/i386/hax/hax-all.c

@@ -209,6 +209,7 @@ int hax_vcpu_destroy(CPUState *cpu)
     CloseHandle(cpu->hThread);
 #endif
     g_free(vcpu);
+    cpu->hax_vcpu = NULL;
     return 0;
 }