[Qemu-devel] [PULL 13/22] virtio: add "use-started" property

["Michael S. Tsirkin" <mst@redhat.com>]

From: Xie Yongji <xieyongji@baidu.com>

In order to avoid migration issues, we introduce a "use-started"
property to the base virtio device to indicate whether use
"started" flag or not. This property will be true by default and
set to false when machine type <= 4.0.

Suggested-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Message-Id: <20190626023130.31315-2-xieyongji@baidu.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/virtio.h | 21 +++++++++++++++++++++
 hw/block/vhost-user-blk.c  |  4 ++--
 hw/core/machine.c          |  1 +
 hw/virtio/virtio.c         | 18 +++++++-----------
 4 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 27c0efc3d0..15d5366939 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -105,6 +105,7 @@ struct VirtIODevice
     uint16_t device_id;
     bool vm_running;
     bool broken; /* device in invalid state, needs reset */
+    bool use_started;
     bool started;
     bool start_on_kick; /* virtio 1.0 transitional devices support that */
     VMChangeStateEntry *vmstate;
@@ -351,4 +352,24 @@ static inline bool virtio_is_big_endian(VirtIODevice *vdev)
     /* Devices conforming to VIRTIO 1.0 or later are always LE. */
     return false;
 }
+
+static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status)
+{
+    if (vdev->use_started) {
+        return vdev->started;
+    }
+
+    return status & VIRTIO_CONFIG_S_DRIVER_OK;
+}
+
+static inline void virtio_set_started(VirtIODevice *vdev, bool started)
+{
+    if (started) {
+        vdev->start_on_kick = false;
+    }
+
+    if (vdev->use_started) {
+        vdev->started = started;
+    }
+}
 #endif
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 9cb61336a6..85bc4017e7 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -191,7 +191,7 @@ static void vhost_user_blk_stop(VirtIODevice *vdev)
 static void vhost_user_blk_set_status(VirtIODevice *vdev, uint8_t status)
 {
     VHostUserBlk *s = VHOST_USER_BLK(vdev);
-    bool should_start = vdev->started;
+    bool should_start = virtio_device_started(vdev, status);
     int ret;
 
     if (!vdev->vm_running) {
@@ -317,7 +317,7 @@ static int vhost_user_blk_connect(DeviceState *dev)
     }
 
     /* restore vhost state */
-    if (vdev->started) {
+    if (virtio_device_started(vdev, vdev->status)) {
         ret = vhost_user_blk_start(vdev);
         if (ret < 0) {
             error_report("vhost-user-blk: vhost start failed: %s",
diff --git a/hw/core/machine.c b/hw/core/machine.c
index ea5a01aa49..ea84bd6788 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -30,6 +30,7 @@ GlobalProperty hw_compat_4_0[] = {
     { "bochs-display",  "edid", "false" },
     { "virtio-vga",     "edid", "false" },
     { "virtio-gpu-pci", "edid", "false" },
+    { "virtio-device", "use-started", "false" },
 };
 const size_t hw_compat_4_0_len = G_N_ELEMENTS(hw_compat_4_0);
 
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index e1e90fcfd6..c9a6ca04b8 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1162,10 +1162,8 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val)
             }
         }
     }
-    vdev->started = val & VIRTIO_CONFIG_S_DRIVER_OK;
-    if (unlikely(vdev->start_on_kick && vdev->started)) {
-        vdev->start_on_kick = false;
-    }
+
+    virtio_set_started(vdev, val & VIRTIO_CONFIG_S_DRIVER_OK);
 
     if (k->set_status) {
         k->set_status(vdev, val);
@@ -1536,8 +1534,7 @@ static bool virtio_queue_notify_aio_vq(VirtQueue *vq)
         ret = vq->handle_aio_output(vdev, vq);
 
         if (unlikely(vdev->start_on_kick)) {
-            vdev->started = true;
-            vdev->start_on_kick = false;
+            virtio_set_started(vdev, true);
         }
     }
 
@@ -1557,8 +1554,7 @@ static void virtio_queue_notify_vq(VirtQueue *vq)
         vq->handle_output(vdev, vq);
 
         if (unlikely(vdev->start_on_kick)) {
-            vdev->started = true;
-            vdev->start_on_kick = false;
+            virtio_set_started(vdev, true);
         }
     }
 }
@@ -1579,8 +1575,7 @@ void virtio_queue_notify(VirtIODevice *vdev, int n)
     }
 
     if (unlikely(vdev->start_on_kick)) {
-        vdev->started = true;
-        vdev->start_on_kick = false;
+        virtio_set_started(vdev, true);
     }
 }
 
@@ -2291,7 +2286,7 @@ static void virtio_vmstate_change(void *opaque, int running, RunState state)
     VirtIODevice *vdev = opaque;
     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
-    bool backend_run = running && vdev->started;
+    bool backend_run = running && virtio_device_started(vdev, vdev->status);
     vdev->vm_running = running;
 
     if (backend_run) {
@@ -2669,6 +2664,7 @@ static void virtio_device_instance_finalize(Object *obj)
 
 static Property virtio_properties[] = {
     DEFINE_VIRTIO_COMMON_FEATURES(VirtIODevice, host_features),
+    DEFINE_PROP_BOOL("use-started", VirtIODevice, use_started, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
MST