On Fri, 04 Mar 2022, Stefano Garzarella wrote: > On Thu, Mar 03, 2022 at 04:01:06PM -0500, Michael S. Tsirkin wrote: > > On Thu, Mar 03, 2022 at 09:14:36PM +0200, Leon Romanovsky wrote: > > > On Thu, Mar 03, 2022 at 03:19:29PM +0000, Lee Jones wrote: > > > > All workers/users should be halted before any clean-up should take place. > > > > > > > > Suggested-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > > > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx> > > > > --- > > > > drivers/vhost/vhost.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > > > index bbaff6a5e21b8..d935d2506963f 100644 > > > > --- a/drivers/vhost/vhost.c > > > > +++ b/drivers/vhost/vhost.c > > > > @@ -693,6 +693,9 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > > > > int i; > > > > > > > > for (i = 0; i < dev->nvqs; ++i) { > > > > + /* Ideally all workers should be stopped prior to clean-up */ > > > > + WARN_ON(mutex_is_locked(&dev->vqs[i]->mutex)); > > > > + > > > > mutex_lock(&dev->vqs[i]->mutex); > > > > > > I know nothing about vhost, but this construction and patch looks > > > strange to me. > > > > > > If all workers were stopped, you won't need mutex_lock(). The mutex_lock > > > here suggests to me that workers can still run here. > > > > > > Thanks > > > > > > "Ideally" here is misleading, we need a bigger detailed comment > > along the lines of: > > > > /* > > * By design, no workers can run here. But if there's a bug and the > > * driver did not flush all work properly then they might, and we > > * encountered such bugs in the past. With no proper flush guest won't > > * work correctly but avoiding host memory corruption in this case > > * sounds like a good idea. > > */ > > Can we use vhost_vq_get_backend() to check this situation? > > IIUC all the vhost devices clear the backend to stop the workers. > This is not racy (if we do after the mutex_lock) and should cover all cases. I can look into this too if you like. -- Lee Jones [李琼斯] Principal Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization