Re: [PATCH v1 5/9] hw/virtio: introduce virtio_device_should_start

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

On Tue, Nov 08, 2022 at 09:23:04AM +0000, Alex Bennée wrote:
> 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 dual 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)
> Fixes: 27ba7b027f (hw/virtio: add boilerplate for vhost-user-gpio device)
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>

why is this in this patchset?

> ---
>  include/hw/virtio/virtio.h   | 18 ++++++++++++++++++
>  hw/block/vhost-user-blk.c    |  6 +-----
>  hw/virtio/vhost-user-fs.c    |  2 +-
>  hw/virtio/vhost-user-gpio.c  |  2 +-
>  hw/virtio/vhost-user-i2c.c   |  2 +-
>  hw/virtio/vhost-user-rng.c   |  2 +-
>  hw/virtio/vhost-user-vsock.c |  2 +-
>  hw/virtio/vhost-vsock.c      |  2 +-
>  8 files changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index f41b4a7e64..3191c618f3 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -389,6 +389,24 @@ 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;
>      }
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index 13bf5cc47a..8feaf12e4e 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/hw/block/vhost-user-blk.c
> @@ -222,14 +222,10 @@ 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 ad0f91c607..1c40f42045 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 8b40fe450c..677d1c7730 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 bc58b6c0d1..864eba695e 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 bc1f36c5ac..8b47287875 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 7b67e29d83..9431b9792c 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 7dc3c73931..aa16d584ee 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) {
> -- 
> 2.34.1