Re: [PATCH V3 3/9] virtio: introduce config op to synchronize vring callbacks

Cornelia Huck
2022-04-28T09:19:48Z

On Mon, Apr 25 2022, Jason Wang <jasowang@redhat.com> wrote:

> This patch introduces new virtio config op to vring
> callbacks. Transport specific method is required to make sure the
> write before this function is visible to the vring_interrupt() that is

Which kind of writes? I.e., what is the scope?

> called after the return of this function. For the transport that
> doesn't provide synchronize_vqs(), use synchornize_rcu() which

Typo: synchronize_rcu()

> synchronize with IRQ implicitly as a fallback.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Halil Pasic <pasic@linux.ibm.com>
> Cc: Cornelia Huck <cohuck@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> include/linux/virtio_config.h | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index b341dd62aa4d..14fe89ff99c7 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -57,6 +57,10 @@ struct virtio_shm_region {
> * include a NULL entry for vqs unused by driver
> * Returns 0 on success or error status
> * @del_vqs: free virtqueues found by find_vqs().
> + * @synchronize_cbs: synchronize with the virtqueue callbacks (optional)
> + * Make sure the writes commited before this method is visible to
> + * vring_interrupt() which is called after this method.

Same here, I think the description needs to be a bit more explicit about
which writes we care about here.

> + * vdev: the virtio_device
> * @get_features: get the array of feature bits for this device.
> * vdev: the virtio_device
> * Returns the first 64 feature bits (all we currently need).
> @@ -89,6 +93,7 @@ struct virtio_config_ops {
> const char * const names[], const bool *ctx,
> struct irq_affinity *desc);
> void (*del_vqs)(struct virtio_device *);
> + void (*synchronize_cbs)(struct virtio_device *);
> u64 (*get_features)(struct virtio_device *vdev);
> int (*finalize_features)(struct virtio_device *vdev);
> const char *(*bus_name)(struct virtio_device *vdev);