unlock iothread mutex before running kvm ioctl

Without this, kvm will hold the mutex while it issues its run ioctl,
and never be able to step out of it, causing a deadlock.

Patchworks-ID: 35359
Signed-off-by: Glauber Costa <glommer@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

3 files changed, 9 insertions, 4 deletions

diff --git a/kvm-all.c b/kvm-all.c
index 5ea0dd8b1..48ae26cae 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -605,7 +605,9 @@ int kvm_cpu_exec(CPUState *env)
         }
 
         kvm_arch_pre_run(env, run);
+        qemu_mutex_unlock_iothread();
         ret = kvm_vcpu_ioctl(env, KVM_RUN, 0);
+        qemu_mutex_lock_iothread();
         kvm_arch_post_run(env, run);
 
         if (ret == -EINTR || ret == -EAGAIN) {
diff --git a/qemu-common.h b/qemu-common.h
index 12e7dd0ad..820dd37a5 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -146,6 +146,9 @@ char *qemu_strndup(const char *str, size_t size);
 void *get_mmap_addr(unsigned long size);
 
 
+void qemu_mutex_lock_iothread(void);
+void qemu_mutex_unlock_iothread(void);
+
 /* Error handling.  */
 
 void QEMU_NORETURN hw_error(const char *fmt, ...)
diff --git a/vl.c b/vl.c
index 374f85be3..afe01af9d 100644
--- a/vl.c
+++ b/vl.c
@@ -3560,8 +3560,8 @@ void qemu_notify_event(void)
     }
 }
 
-#define qemu_mutex_lock_iothread() do { } while (0)
-#define qemu_mutex_unlock_iothread() do { } while (0)
+void qemu_mutex_lock_iothread(void) {}
+void qemu_mutex_unlock_iothread(void) {}
 
 void vm_stop(int reason)
 {
@@ -3760,7 +3760,7 @@ static void qemu_signal_lock(unsigned int msecs)
     qemu_mutex_unlock(&qemu_fair_mutex);
 }
 
-static void qemu_mutex_lock_iothread(void)
+void qemu_mutex_lock_iothread(void)
 {
     if (kvm_enabled()) {
         qemu_mutex_lock(&qemu_fair_mutex);
@@ -3770,7 +3770,7 @@ static void qemu_mutex_lock_iothread(void)
         qemu_signal_lock(100);
 }
 
-static void qemu_mutex_unlock_iothread(void)
+void qemu_mutex_unlock_iothread(void)
 {
     qemu_mutex_unlock(&qemu_global_mutex);
 }