Re: [PATCH v2 03/20] virtio: Add get_shm_region method

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Aug 07, 2020 at 03:55:09PM -0400, Vivek Goyal wrote:
> From: Sebastien Boeuf <sebastien.boeuf@intel.com>
> 
> Virtio defines 'shared memory regions' that provide a continuously
> shared region between the host and guest.
> 
> Provide a method to find a particular region on a device.
> 
> Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: kvm@vger.kernel.org
> Cc: "Michael S. Tsirkin" <mst@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  include/linux/virtio_config.h | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index bb4cc4910750..c859f000a751 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -10,6 +10,11 @@
>  
>  struct irq_affinity;
>  
> +struct virtio_shm_region {
> +       u64 addr;
> +       u64 len;
> +};
> +
>  /**
>   * virtio_config_ops - operations for configuring a virtio device
>   * Note: Do not assume that a transport implements all of the operations
> @@ -65,6 +70,7 @@ struct irq_affinity;
>   *      the caller can then copy.
>   * @set_vq_affinity: set the affinity for a virtqueue (optional).
>   * @get_vq_affinity: get the affinity for a virtqueue (optional).
> + * @get_shm_region: get a shared memory region based on the index.
>   */
>  typedef void vq_callback_t(struct virtqueue *);
>  struct virtio_config_ops {
> @@ -88,6 +94,8 @@ struct virtio_config_ops {
>  			       const struct cpumask *cpu_mask);
>  	const struct cpumask *(*get_vq_affinity)(struct virtio_device *vdev,
>  			int index);
> +	bool (*get_shm_region)(struct virtio_device *vdev,
> +			       struct virtio_shm_region *region, u8 id);
>  };
>  
>  /* If driver didn't advertise the feature, it will never appear. */
> @@ -250,6 +258,15 @@ int virtqueue_set_affinity(struct virtqueue *vq, const struct cpumask *cpu_mask)
>  	return 0;
>  }
>  
> +static inline
> +bool virtio_get_shm_region(struct virtio_device *vdev,
> +                         struct virtio_shm_region *region, u8 id)
> +{
> +	if (!vdev->config->get_shm_region)
> +		return false;
> +	return vdev->config->get_shm_region(vdev, region, id);
> +}
> +
>  static inline bool virtio_is_little_endian(struct virtio_device *vdev)
>  {
>  	return virtio_has_feature(vdev, VIRTIO_F_VERSION_1) ||
> -- 
> 2.25.4
>