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

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

From: Jan Kiszka <jan.kiszka@siemens.com>

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 <jan.kiszka@siemens.com>
---
 cpus.c |   13 +++++++++----
 cpus.h |    1 +
 vl.c   |    1 +
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/cpus.c b/cpus.c
index 9bf5224..925a40f 100644
--- a/cpus.c
+++ b/cpus.c
@@ -99,6 +99,14 @@ void cpu_synchronize_all_post_init(void)
     }
 }
 
+void cpu_stop_current(void)
+{
+    if (cpu_single_env) {
+        cpu_single_env->stopped = 1;
+        cpu_exit(cpu_single_env);
+    }
+}
+
 int cpu_is_stopped(CPUState *env)
 {
     return !vm_running || env->stopped;
@@ -854,10 +862,7 @@ 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 fa3f165..e021126 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 193afba..2b9a9da 100644
--- a/vl.c
+++ b/vl.c
@@ -1278,6 +1278,7 @@ void qemu_system_reset_request(void)
     } else {
         reset_requested = 1;
     }
+    cpu_stop_current();
     qemu_notify_event();
 }
 
-- 
1.7.1