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

["Jiang, Cheng1" <cheng1.jiang@intel.com>]

Hi Gavin,

> -----Original Message-----
> From: Gavin Hu [mailto:Gavin.Hu@arm.com]
> Sent: Wednesday, December 18, 2019 5:52 PM
> To: Jiang, Cheng1 <cheng1.jiang@intel.com>; maxime.coquelin@redhat.com;
> Bie, Tiwei <tiwei.bie@intel.com>; Wang, Zhihong
> <zhihong.wang@intel.com>; Liu, Yong <yong.liu@intel.com>
> Cc: dev@dpdk.org; nd <nd@arm.com>
> Subject: RE: [dpdk-dev] [PATCH v2] net/virtio: packed ring notification data
> feature support
> 
> 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"?

It makes more sense. I will add more specific commit log in the next version. Thank you.

> >
> > 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?

Sure, you're right. I'll modify the patch in the next version. 

Thanks again.
Cheng

> > +				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