[PATCH 3/11] QEMU/KVM: Proper vm_stop on debug events

[Jan Kiszka <jan.kiszka@web.de>]

[ Changes to last revision: Reordered kvm_debug_stop_requested and
  vm_stop to avoid race. ]

When a vcpu exits after hitting a debug exception, we have to invoke
vm_stop(EXCP_DEBUG). But this has to take place over the io-thread.

This patch introduces kvm_debug_stop_requested to signal this event, and
it takes care that the interrupted vcpu itself goes immediately into
stop state.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
---
 qemu/qemu-kvm.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Index: b/qemu/qemu-kvm.c
===================================================================
--- a/qemu/qemu-kvm.c
+++ b/qemu/qemu-kvm.c
@@ -58,6 +58,8 @@ pthread_t io_thread;
 static int io_thread_fd = -1;
 static int io_thread_sigfd = -1;
 
+static int kvm_debug_stop_requested;
+
 static inline unsigned long kvm_get_thread_id(void)
 {
     return syscall(SYS_gettid);
@@ -517,6 +519,10 @@ int kvm_main_loop(void)
             qemu_system_powerdown();
         else if (qemu_reset_requested())
 	    qemu_kvm_system_reset();
+	else if (kvm_debug_stop_requested) {
+	    vm_stop(EXCP_DEBUG);
+	    kvm_debug_stop_requested = 0;
+	}
     }
 
     pause_all_threads();
@@ -529,7 +535,8 @@ static int kvm_debug(void *opaque, int v
 {
     CPUState *env = cpu_single_env;
 
-    env->exception_index = EXCP_DEBUG;
+    kvm_debug_stop_requested = 1;
+    vcpu_info[vcpu].stopped = 1;
     return 1;
 }