Re: [dpdk-dev] [PATCH v2] net/virtio: packed ring notification data feature support

[Gavin Hu <Gavin.Hu@arm.com>]

Hi Jiang,

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Cheng Jiang
> Sent: Wednesday, December 18, 2019 4:17 PM
> To: maxime.coquelin@redhat.com; tiwei.bie@intel.com;
> zhihong.wang@intel.com; yong.liu@intel.com
> Cc: dev@dpdk.org; Cheng Jiang <Cheng1.jiang@intel.com>
> Subject: [dpdk-dev] [PATCH v2] net/virtio: packed ring notification data
> feature support
> 
> This patch supports the feature that the driver passes extra data
> (besides identifying the virtqueue) in its device notifications.
Can the commit log be more specific about the extra data? Something like "expand the notification to include the avail index and avail wrap counter, if any"? 
> 
> Signed-off-by: Cheng Jiang <Cheng1.jiang@intel.com>
> ---
> 
> v2:
> * Removed rte_unused attribute in *hw.
> * Added some comments on notify_data.
> 
>  drivers/net/virtio/virtio_ethdev.h |  3 ++-
>  drivers/net/virtio/virtio_pci.c    | 27 +++++++++++++++++++++++++--
>  drivers/net/virtio/virtio_pci.h    |  6 ++++++
>  3 files changed, 33 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.h
> b/drivers/net/virtio/virtio_ethdev.h
> index a10111758..cd8947656 100644
> --- a/drivers/net/virtio/virtio_ethdev.h
> +++ b/drivers/net/virtio/virtio_ethdev.h
> @@ -36,7 +36,8 @@
>  	 1ULL << VIRTIO_F_IN_ORDER        |	\
>  	 1ULL << VIRTIO_F_RING_PACKED	  |	\
>  	 1ULL << VIRTIO_F_IOMMU_PLATFORM  |	\
> -	 1ULL << VIRTIO_F_ORDER_PLATFORM)
> +	 1ULL << VIRTIO_F_ORDER_PLATFORM  |	\
> +	 1ULL << VIRTIO_F_NOTIFICATION_DATA)
> 
>  #define VIRTIO_PMD_SUPPORTED_GUEST_FEATURES	\
>  	(VIRTIO_PMD_DEFAULT_GUEST_FEATURES |	\
> diff --git a/drivers/net/virtio/virtio_pci.c b/drivers/net/virtio/virtio_pci.c
> index 4468e89cb..8b4e001a1 100644
> --- a/drivers/net/virtio/virtio_pci.c
> +++ b/drivers/net/virtio/virtio_pci.c
> @@ -416,9 +416,32 @@ modern_del_queue(struct virtio_hw *hw, struct
> virtqueue *vq)
>  }
> 
>  static void
> -modern_notify_queue(struct virtio_hw *hw __rte_unused, struct virtqueue
> *vq)
> +modern_notify_queue(struct virtio_hw *hw, struct virtqueue *vq)
>  {
> -	rte_write16(vq->vq_queue_index, vq->notify_addr);
> +	uint32_t notify_data;
> +
> +	if (!vtpci_with_feature(hw, VIRTIO_F_NOTIFICATION_DATA)) {
> +		rte_write16(vq->vq_queue_index, vq->notify_addr);
> +		return;
> +	}
> +
> +	if (vtpci_with_feature(hw, VIRTIO_F_RING_PACKED)) {
> +		/*
> +		 * Bit[0:15]: vq queue index
> +		 * Bit[16:30]: avail index
> +		 * Bit[31]: avail wrap counter
> +		 */
> +		notify_data = ((((uint32_t)vq-
> >vq_packed.used_wrap_counter << 15) |
Why not do ' used_wrap_counter << 31' to be more straightforward and matches the above comment?  
> +				vq->vq_avail_idx) << 16) | vq-
> >vq_queue_index;

> +	} else {
> +		/*
> +		 * Bit[0:15]: vq queue index
> +		 * Bit[16:31]: avail index
> +		 */
> +		notify_data = ((uint32_t)vq->vq_avail_idx << 16) |
> +				vq->vq_queue_index;
> +	}
> +	rte_write32(notify_data, vq->notify_addr);
>  }
> 
>  const struct virtio_pci_ops modern_ops = {
> diff --git a/drivers/net/virtio/virtio_pci.h b/drivers/net/virtio/virtio_pci.h
> index a38cb45ad..7433d2f08 100644
> --- a/drivers/net/virtio/virtio_pci.h
> +++ b/drivers/net/virtio/virtio_pci.h
> @@ -135,6 +135,12 @@ struct virtnet_ctl;
>   */
>  #define VIRTIO_F_ORDER_PLATFORM 36
> 
> +/*
> + * This feature indicates that the driver passes extra data (besides
> + * identifying the virtqueue) in its device notifications.
> + */
> +#define VIRTIO_F_NOTIFICATION_DATA 38
> +
>  /* The Guest publishes the used index for which it expects an interrupt
>   * at the end of the avail ring. Host should ignore the avail->flags field. */
>  /* The Host publishes the avail index for which it expects a kick
> --
> 2.17.1