hw/virtio: introduce virtio_device_should_start

The previous fix to virtio_device_started revealed a problem in its
use by both the core and the device code. The core code should be able
to handle the device "starting" while the VM isn't running to handle
the restoration of migration state. To solve this duel use introduce a
new helper for use by the vhost-user backends who all use it to feed a
should_start variable.

We can also pick up a change vhost_user_blk_set_status while we are at
it which follows the same pattern.

Fixes: 9f6bcfd99f (hw/virtio: move vm_running check to virtio_device_started)
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Message-Id: <20221107121407.1010913-1-alex.bennee@linaro.org>

8 files changed, 25 insertions, 11 deletions

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 28409c9..16ad400 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -226,14 +226,10 @@ 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 = virtio_device_started(vdev, status);
+    bool should_start = virtio_device_should_start(vdev, status);
     Error *local_err = NULL;
     int ret;
 
-    if (!vdev->vm_running) {
-        should_start = false;
-    }
-
     if (!s->connected) {
         return;
     }
diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
index ad0f91c..1c40f42 100644
--- a/hw/virtio/vhost-user-fs.c
+++ b/hw/virtio/vhost-user-fs.c
@@ -123,7 +123,7 @@ static void vuf_stop(VirtIODevice *vdev)
 static void vuf_set_status(VirtIODevice *vdev, uint8_t status)
 {
     VHostUserFS *fs = VHOST_USER_FS(vdev);
-    bool should_start = virtio_device_started(vdev, status);
+    bool should_start = virtio_device_should_start(vdev, status);
 
     if (vhost_dev_is_started(&fs->vhost_dev) == should_start) {
         return;
diff --git a/hw/virtio/vhost-user-gpio.c b/hw/virtio/vhost-user-gpio.c
index 8b40fe4..677d1c7 100644
--- a/hw/virtio/vhost-user-gpio.c
+++ b/hw/virtio/vhost-user-gpio.c
@@ -152,7 +152,7 @@ static void vu_gpio_stop(VirtIODevice *vdev)
 static void vu_gpio_set_status(VirtIODevice *vdev, uint8_t status)
 {
     VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
-    bool should_start = virtio_device_started(vdev, status);
+    bool should_start = virtio_device_should_start(vdev, status);
 
     trace_virtio_gpio_set_status(status);
 
diff --git a/hw/virtio/vhost-user-i2c.c b/hw/virtio/vhost-user-i2c.c
index bc58b6c..864eba6 100644
--- a/hw/virtio/vhost-user-i2c.c
+++ b/hw/virtio/vhost-user-i2c.c
@@ -93,7 +93,7 @@ static void vu_i2c_stop(VirtIODevice *vdev)
 static void vu_i2c_set_status(VirtIODevice *vdev, uint8_t status)
 {
     VHostUserI2C *i2c = VHOST_USER_I2C(vdev);
-    bool should_start = virtio_device_started(vdev, status);
+    bool should_start = virtio_device_should_start(vdev, status);
 
     if (vhost_dev_is_started(&i2c->vhost_dev) == should_start) {
         return;
diff --git a/hw/virtio/vhost-user-rng.c b/hw/virtio/vhost-user-rng.c
index bc1f36c..8b47287 100644
--- a/hw/virtio/vhost-user-rng.c
+++ b/hw/virtio/vhost-user-rng.c
@@ -90,7 +90,7 @@ static void vu_rng_stop(VirtIODevice *vdev)
 static void vu_rng_set_status(VirtIODevice *vdev, uint8_t status)
 {
     VHostUserRNG *rng = VHOST_USER_RNG(vdev);
-    bool should_start = virtio_device_started(vdev, status);
+    bool should_start = virtio_device_should_start(vdev, status);
 
     if (vhost_dev_is_started(&rng->vhost_dev) == should_start) {
         return;
diff --git a/hw/virtio/vhost-user-vsock.c b/hw/virtio/vhost-user-vsock.c
index 7b67e29..9431b97 100644
--- a/hw/virtio/vhost-user-vsock.c
+++ b/hw/virtio/vhost-user-vsock.c
@@ -55,7 +55,7 @@ const VhostDevConfigOps vsock_ops = {
 static void vuv_set_status(VirtIODevice *vdev, uint8_t status)
 {
     VHostVSockCommon *vvc = VHOST_VSOCK_COMMON(vdev);
-    bool should_start = virtio_device_started(vdev, status);
+    bool should_start = virtio_device_should_start(vdev, status);
 
     if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) {
         return;
diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
index 7dc3c73..aa16d58 100644
--- a/hw/virtio/vhost-vsock.c
+++ b/hw/virtio/vhost-vsock.c
@@ -70,7 +70,7 @@ static int vhost_vsock_set_running(VirtIODevice *vdev, int start)
 static void vhost_vsock_set_status(VirtIODevice *vdev, uint8_t status)
 {
     VHostVSockCommon *vvc = VHOST_VSOCK_COMMON(vdev);
-    bool should_start = virtio_device_started(vdev, status);
+    bool should_start = virtio_device_should_start(vdev, status);
     int ret;
 
     if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) {
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 1423dba..141a253 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -395,6 +395,24 @@ static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status)
         return vdev->started;
     }
 
+    return status & VIRTIO_CONFIG_S_DRIVER_OK;
+}
+
+/**
+ * virtio_device_should_start() - check if device startable
+ * @vdev - the VirtIO device
+ * @status - the devices status bits
+ *
+ * This is similar to virtio_device_started() but also encapsulates a
+ * check on the VM status which would prevent a device starting
+ * anyway.
+ */
+static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status)
+{
+    if (vdev->use_started) {
+        return vdev->started;
+    }
+
     if (!vdev->vm_running) {
         return false;
     }