[Qemu-devel] [PATCH 02/37] Stop current VCPU on synchronous reset requests

[Marcelo Tosatti]

From: Jan Kiszka <address@hidden>

If some I/O operation ends up calling qemu_system_reset_request in VCPU
context, we record this and inform the io-thread, but we do not
terminate the VCPU loop. This can lead to fairly unexpected behavior if
the triggering reset operation is supposed to work synchronously.

Fix this for TCG (when run in deterministic I/O mode) by setting the
VCPU on stop and issuing a cpu_exit. KVM requires some more work on its
VCPU loop.

[ ported from qemu-kvm ]

Signed-off-by: Jan Kiszka <address@hidden>
Signed-off-by: Marcelo Tosatti <address@hidden>
---
 cpus.c |   17 +++++++++++++----
 cpus.h |    1 +
 vl.c   |    1 +
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/cpus.c b/cpus.c
index ab6e40e..f8a88e3 100644
--- a/cpus.c
+++ b/cpus.c
@@ -312,6 +312,10 @@ void qemu_notify_event(void)
 void qemu_mutex_lock_iothread(void) {}
 void qemu_mutex_unlock_iothread(void) {}
 
+void cpu_stop_current(void)
+{
+}
+
 void vm_stop(int reason)
 {
     do_vm_stop(reason);
@@ -852,6 +856,14 @@ static void qemu_system_vmstop_request(int reason)
     qemu_notify_event();
 }
 
+void cpu_stop_current(void)
+{
+    if (cpu_single_env) {
+        cpu_single_env->stopped = 1;
+        cpu_exit(cpu_single_env);
+    }
+}
+
 void vm_stop(int reason)
 {
     QemuThread me;
@@ -863,10 +875,7 @@ void vm_stop(int reason)
          * FIXME: should not return to device code in case
          * vm_stop() has been requested.
          */
-        if (cpu_single_env) {
-            cpu_exit(cpu_single_env);
-            cpu_single_env->stop = 1;
-        }
+        cpu_stop_current();
         return;
     }
     do_vm_stop(reason);
diff --git a/cpus.h b/cpus.h
index bf4d9bb..4cadb64 100644
--- a/cpus.h
+++ b/cpus.h
@@ -6,6 +6,7 @@ int qemu_init_main_loop(void);
 void qemu_main_loop_start(void);
 void resume_all_vcpus(void);
 void pause_all_vcpus(void);
+void cpu_stop_current(void);
 
 /* vl.c */
 extern int smp_cores;
diff --git a/vl.c b/vl.c
index ed2cdfa..5e3f7f2 100644
--- a/vl.c
+++ b/vl.c
@@ -1296,6 +1296,7 @@ void qemu_system_reset_request(void)
     } else {
         reset_requested = 1;
     }
+    cpu_stop_current();
     qemu_notify_event();
 }
 
-- 
1.7.4