Re: [PATCH v4 10/22] hw/virtio: move vm_running check to virtio_device_started

[Michael S. Tsirkin]

On Thu, Nov 03, 2022 at 07:18:30PM +0000, Alex Bennée wrote:
> 
> "Michael S. Tsirkin" <mst@redhat.com> writes:
> 
> > On Tue, Aug 02, 2022 at 10:49:58AM +0100, Alex Bennée wrote:
> >> All the boilerplate virtio code does the same thing (or should at
> >> least) of checking to see if the VM is running before attempting to
> >> start VirtIO. Push the logic up to the common function to avoid
> >> getting a copy and paste wrong.
> >> 
> >> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> >
> > How bad is it if we drop this?
> 
> 
> I assume it will break gpio. Why do we want to drop this now? It has
> been merged awhile. However there was a follow-up patch which tweaked
> the order of checks in virtio_device_started.

And that follow up patch trips up UBSAN:

https://gitlab.com/mitsirkin/qemu/-/pipelines/684763327




> >
> >> ---
> >>  include/hw/virtio/virtio.h   | 5 +++++
> >>  hw/virtio/vhost-user-fs.c    | 6 +-----
> >>  hw/virtio/vhost-user-i2c.c   | 6 +-----
> >>  hw/virtio/vhost-user-rng.c   | 6 +-----
> >>  hw/virtio/vhost-user-vsock.c | 6 +-----
> >>  hw/virtio/vhost-vsock.c      | 6 +-----
> >>  6 files changed, 10 insertions(+), 25 deletions(-)
> >> 
> >> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> >> index 9bb2485415..74e7ad5a92 100644
> >> --- a/include/hw/virtio/virtio.h
> >> +++ b/include/hw/virtio/virtio.h
> >> @@ -100,6 +100,7 @@ struct VirtIODevice
> >>      VirtQueue *vq;
> >>      MemoryListener listener;
> >>      uint16_t device_id;
> >> +    /* @vm_running: current VM running state via virtio_vmstate_change() 
> >> */
> >>      bool vm_running;
> >>      bool broken; /* device in invalid state, needs reset */
> >>      bool use_disabled_flag; /* allow use of 'disable' flag when needed */
> >> @@ -376,6 +377,10 @@ static inline bool virtio_device_started(VirtIODevice 
> >> *vdev, uint8_t status)
> >>          return vdev->started;
> >>      }
> >>  
> >> +    if (!vdev->vm_running) {
> >> +        return false;
> >> +    }
> >> +
> >>      return status & VIRTIO_CONFIG_S_DRIVER_OK;
> >>  }
> >>  
> >> diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
> >> index e513e4fdda..d2bebba785 100644
> >> --- a/hw/virtio/vhost-user-fs.c
> >> +++ b/hw/virtio/vhost-user-fs.c
> >> @@ -122,11 +122,7 @@ 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 = status & VIRTIO_CONFIG_S_DRIVER_OK;
> >> -
> >> -    if (!vdev->vm_running) {
> >> -        should_start = false;
> >> -    }
> >> +    bool should_start = virtio_device_started(vdev, status);
> >>  
> >>      if (fs->vhost_dev.started == should_start) {
> >>          return;
> >> diff --git a/hw/virtio/vhost-user-i2c.c b/hw/virtio/vhost-user-i2c.c
> >> index 6020eee093..b930cf6d5e 100644
> >> --- a/hw/virtio/vhost-user-i2c.c
> >> +++ b/hw/virtio/vhost-user-i2c.c
> >> @@ -93,11 +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 = status & VIRTIO_CONFIG_S_DRIVER_OK;
> >> -
> >> -    if (!vdev->vm_running) {
> >> -        should_start = false;
> >> -    }
> >> +    bool should_start = virtio_device_started(vdev, status);
> >>  
> >>      if (i2c->vhost_dev.started == should_start) {
> >>          return;
> >> diff --git a/hw/virtio/vhost-user-rng.c b/hw/virtio/vhost-user-rng.c
> >> index 3a7bf8e32d..a9c1c4bc79 100644
> >> --- a/hw/virtio/vhost-user-rng.c
> >> +++ b/hw/virtio/vhost-user-rng.c
> >> @@ -90,11 +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 = status & VIRTIO_CONFIG_S_DRIVER_OK;
> >> -
> >> -    if (!vdev->vm_running) {
> >> -        should_start = false;
> >> -    }
> >> +    bool should_start = virtio_device_started(vdev, status);
> >>  
> >>      if (rng->vhost_dev.started == should_start) {
> >>          return;
> >> diff --git a/hw/virtio/vhost-user-vsock.c b/hw/virtio/vhost-user-vsock.c
> >> index 0f8ff99f85..22c1616ebd 100644
> >> --- a/hw/virtio/vhost-user-vsock.c
> >> +++ b/hw/virtio/vhost-user-vsock.c
> >> @@ -55,11 +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 = status & VIRTIO_CONFIG_S_DRIVER_OK;
> >> -
> >> -    if (!vdev->vm_running) {
> >> -        should_start = false;
> >> -    }
> >> +    bool should_start = virtio_device_started(vdev, status);
> >>  
> >>      if (vvc->vhost_dev.started == should_start) {
> >>          return;
> >> diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
> >> index 0338de892f..8031c164a5 100644
> >> --- a/hw/virtio/vhost-vsock.c
> >> +++ b/hw/virtio/vhost-vsock.c
> >> @@ -70,13 +70,9 @@ 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 = status & VIRTIO_CONFIG_S_DRIVER_OK;
> >> +    bool should_start = virtio_device_started(vdev, status);
> >>      int ret;
> >>  
> >> -    if (!vdev->vm_running) {
> >> -        should_start = false;
> >> -    }
> >> -
> >>      if (vvc->vhost_dev.started == should_start) {
> >>          return;
> >>      }
> >> -- 
> >> 2.30.2
> 
> 
> -- 
> Alex Bennée