[v13,02/10] net/virtio: add packed virtqueue helpers

  Add helper functions to set/clear and check descriptor flags.

Signed-off-by: Jens Freimann <jfreimann@redhat.com>
---
 drivers/net/virtio/virtio_pci.h |  6 +++
 drivers/net/virtio/virtqueue.h  | 91 ++++++++++++++++++++++++++++++++-
 2 files changed, 95 insertions(+), 2 deletions(-)
  

On 12/14/18 4:59 PM, Jens Freimann wrote:
> Add helper functions to set/clear and check descriptor flags.
> 
> Signed-off-by: Jens Freimann <jfreimann@redhat.com>
> ---
>   drivers/net/virtio/virtio_pci.h |  6 +++
>   drivers/net/virtio/virtqueue.h  | 91 ++++++++++++++++++++++++++++++++-
>   2 files changed, 95 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_pci.h b/drivers/net/virtio/virtio_pci.h
> index 4c975a531..b22b62dad 100644
> --- a/drivers/net/virtio/virtio_pci.h
> +++ b/drivers/net/virtio/virtio_pci.h
> @@ -315,6 +315,12 @@ vtpci_with_feature(struct virtio_hw *hw, uint64_t bit)
>   	return (hw->guest_features & (1ULL << bit)) != 0;
>   }
>   
> +static inline int
> +vtpci_packed_queue(struct virtio_hw *hw)
> +{
> +	return vtpci_with_feature(hw, VIRTIO_F_RING_PACKED);
> +}
> +
>   /*
>    * Function declaration from virtio_pci.c
>    */
> diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
> index d4e0858e4..19fabae0b 100644
> --- a/drivers/net/virtio/virtqueue.h
> +++ b/drivers/net/virtio/virtqueue.h
> @@ -251,6 +251,44 @@ struct virtio_tx_region {
>   			   __attribute__((__aligned__(16)));
>   };
>   
> +static inline void
> +_set_desc_avail(struct vring_packed_desc *desc, int wrap_counter)
> +{
> +	desc->flags |= VRING_DESC_F_AVAIL(wrap_counter) |
> +		       VRING_DESC_F_USED(!wrap_counter);
> +}
> +
> +static inline void
> +set_desc_avail(struct virtqueue *vq, struct vring_packed_desc *desc)
> +{
> +	_set_desc_avail(desc, vq->avail_wrap_counter);
> +}
> +
> +static inline int
> +desc_is_used(struct vring_packed_desc *desc, struct virtqueue *vq)
> +{
> +	uint16_t used, avail, flags;
> +
> +	flags = desc->flags;
> +	used = !!(flags & VRING_DESC_F_USED(1));
> +	avail = !!(flags & VRING_DESC_F_AVAIL(1));
> +
> +	return avail == used && used == vq->used_wrap_counter;
> +}
> +
> +
> +static inline void
> +vring_desc_init_packed(struct virtqueue *vq, int n)
> +{
> +	int i;
> +	for (i = 0; i < n - 1; i++) {
> +		vq->ring_packed.desc_packed[i].id = i;
> +		vq->vq_descx[i].next = i + 1;
> +	}
> +	vq->ring_packed.desc_packed[i].id = i;
> +	vq->vq_descx[i].next = VQ_RING_DESC_CHAIN_END;
> +}
> +
>   /* Chain all the descriptors in the ring with an END */
>   static inline void
>   vring_desc_init(struct vring_desc *dp, uint16_t n)
> @@ -262,13 +300,59 @@ vring_desc_init(struct vring_desc *dp, uint16_t n)
>   	dp[i].next = VQ_RING_DESC_CHAIN_END;
>   }
>   
> +/**
> + * Tell the backend not to interrupt us.
> + */
> +static inline void
> +virtqueue_disable_intr_packed(struct virtqueue *vq)
> +{
> +	uint16_t *event_flags = &vq->ring_packed.driver_event->desc_event_flags;
> +
> +	if (*event_flags != RING_EVENT_FLAGS_DISABLE)
> +		*event_flags = RING_EVENT_FLAGS_DISABLE;

Why not just setting the value unconditionally?
IIUC, it is not called in the hot path?

> +}
> +
> +
>   /**
>    * Tell the backend not to interrupt us.
>    */
>   static inline void
>   virtqueue_disable_intr(struct virtqueue *vq)
>   {
> -	vq->vq_ring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
> +	if (vtpci_packed_queue(vq->hw))
> +		virtqueue_disable_intr_packed(vq);
> +	else
> +		vq->vq_ring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
> +}
> +
> +/**
> + * Tell the backend to interrupt. Implementation for packed virtqueues.
> + */
> +static inline void
> +virtqueue_enable_intr_packed(struct virtqueue *vq)
> +{
> +	uint16_t *off_wrap = &vq->ring_packed.driver_event->desc_event_off_wrap;
> +	uint16_t *event_flags = &vq->ring_packed.driver_event->desc_event_flags;
> +
> +	*off_wrap = vq->vq_used_cons_idx |
> +		((uint16_t)(vq->used_wrap_counter << 15));

Don't we want to set off_wrap only if VIRTIO_RING_F_EVENT_IDX
negotiated?

> +
> +	if (vq->event_flags_shadow == RING_EVENT_FLAGS_DISABLE) {
> +		virtio_wmb();
> +		vq->event_flags_shadow =
> +			vtpci_with_feature(vq->hw, VIRTIO_RING_F_EVENT_IDX) ?
> +				RING_EVENT_FLAGS_DESC : RING_EVENT_FLAGS_ENABLE;
> +		*event_flags = vq->event_flags_shadow;
> +	}
> +}
> +
> +/**
> + * Tell the backend to interrupt. Implementation for split virtqueues.
> + */
> +static inline void
> +virtqueue_enable_intr_split(struct virtqueue *vq)
> +{
> +	vq->vq_ring.avail->flags &= (~VRING_AVAIL_F_NO_INTERRUPT);
>   }
>   
>   /**
> @@ -277,7 +361,10 @@ virtqueue_disable_intr(struct virtqueue *vq)
>   static inline void
>   virtqueue_enable_intr(struct virtqueue *vq)
>   {
> -	vq->vq_ring.avail->flags &= (~VRING_AVAIL_F_NO_INTERRUPT);
> +	if (vtpci_packed_queue(vq->hw))
> +		virtqueue_enable_intr_packed(vq);
> +	else
> +		virtqueue_enable_intr_split(vq);
>   }
>   
>   /**
>
  

On 12/14/18 4:59 PM, Jens Freimann wrote:
> +static inline void
> +_set_desc_avail(struct vring_packed_desc *desc, int wrap_counter)
> +{
> +	desc->flags |= VRING_DESC_F_AVAIL(wrap_counter) |
> +		       VRING_DESC_F_USED(!wrap_counter);
> +}
> +
> +static inline void
> +set_desc_avail(struct virtqueue *vq, struct vring_packed_desc *desc)
> +{
> +	_set_desc_avail(desc, vq->avail_wrap_counter);
> +}
> +

I wonder whether these helpers are really needed, as they are no more
used in virtio_rxtx.c.

Only _set_desc_avail() is used for the ctrl vq.