[Qemu-devel] [PATCH 5/5] virtio: add "use-started" property

[elohimes]

From: Xie Yongji <address@hidden>

In order to avoid migration issues, we introduce a "use-started"
property to the base virtio device to indicate whether "started"
and "start_on_kick" flag could be used. This property will be
true by default and set to false when machine type <= 4.0.

Suggested-by: Greg Kurz <address@hidden>
Signed-off-by: Xie Yongji <address@hidden>
---
 hw/block/vhost-user-blk.c  |  8 ++++++--
 hw/core/machine.c          |  4 +++-
 hw/virtio/virtio.c         |  7 ++++---
 include/hw/virtio/virtio.h | 10 ++++++++++
 4 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 9cb61336a6..520c5d3d4b 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -191,9 +191,13 @@ 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 = status & VIRTIO_CONFIG_S_DRIVER_OK;
     int ret;
 
+    if (virtio_device_started(vdev)) {
+        should_start = true;
+    }
+
     if (!vdev->vm_running) {
         should_start = false;
     }
@@ -317,7 +321,7 @@ static int vhost_user_blk_connect(DeviceState *dev)
     }
 
     /* restore vhost state */
-    if (vdev->started) {
+    if (virtio_device_started(vdev)) {
         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 934c1bcceb..1730d28c1b 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -24,7 +24,9 @@
 #include "hw/pci/pci.h"
 #include "hw/mem/nvdimm.h"
 
-GlobalProperty hw_compat_4_0[] = {};
+GlobalProperty hw_compat_4_0[] = {
+    { "virtio-device", "use-started", "false" },
+};
 const size_t hw_compat_4_0_len = G_N_ELEMENTS(hw_compat_4_0);
 
 GlobalProperty hw_compat_3_1[] = {
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 9e17293d46..4c05a9efe3 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1803,14 +1803,14 @@ static bool virtio_started_needed(void *opaque)
 {
     VirtIODevice *vdev = opaque;
 
-    return vdev->started;
+    return vdev->started && vdev->use_started;
 }
 
 static bool virtio_start_on_kick_needed(void *opaque)
 {
     VirtIODevice *vdev = opaque;
 
-    return vdev->start_on_kick;
+    return vdev->start_on_kick && vdev->use_started;
 }
 
 static const VMStateDescription vmstate_virtqueue = {
@@ -2320,7 +2320,7 @@ 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->vm_running = running;
 
     if (backend_run) {
@@ -2698,6 +2698,7 @@ 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(),
 };
 
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 27c0efc3d0..ba4dbd7480 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 +352,13 @@ 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)
+{
+    if (vdev->use_started) {
+        return vdev->started;
+    }
+
+    return vdev->status & VIRTIO_CONFIG_S_DRIVER_OK;
+}
 #endif
-- 
2.17.1