On Wed, Apr 06, 2022 at 04:35:36PM +0800, Jason Wang wrote:
> This patch introduce
introduces
> a new
new
> virtio config ops to vring
> callbacks. Transport specific method is required to call
> synchornize_irq() on the IRQs. For the transport that doesn't provide
> synchronize_vqs(), use synchornize_rcu() as a fallback.
>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> include/linux/virtio_config.h | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index b341dd62aa4d..08b73d9bbff2 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -57,6 +57,8 @@ 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_vqs: synchronize with the virtqueue callbacks.
> + * vdev: the virtio_device
I think I prefer synchronize_callbacks
> * @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 +91,7 @@ struct virtio_config_ops {
> const char * const names[], const bool *ctx,
> struct irq_affinity *desc);
> void (*del_vqs)(struct virtio_device *);
> + void (*synchronize_vqs)(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);
> @@ -217,6 +220,19 @@ int virtio_find_vqs_ctx(struct virtio_device *vdev, unsigned nvqs,
> desc);
> }
>
> +/**
> + * virtio_synchronize_vqs - synchronize with virtqueue callbacks
> + * @vdev: the device
> + */
> +static inline
> +void virtio_synchronize_vqs(struct virtio_device *dev)
> +{
> + if (dev->config->synchronize_vqs)
> + dev->config->synchronize_vqs(dev);
> + else
> + synchronize_rcu();
I am not sure about this fallback and the latency impact.
Maybe synchronize_rcu_expedited is better here.
> +}
> +
> /**
> * virtio_device_ready - enable vq use in probe function
> * @vdev: the device
> --
> 2.25.1
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