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

[Michael S. Tsirkin]

On Thu, Nov 03, 2022 at 04:30:48PM -0400, Michael S. Tsirkin wrote:
> 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
> 


And more specifically this

https://gitlab.com/mitsirkin/qemu/-/jobs/3269957848

> 
> 
> > >
> > >> ---
> > >>  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