Hi,
> -----Original Message-----
> From: Chen, Junjie J
> Sent: Wednesday, December 27, 2017 1:43 AM
> To: Wang, Xiao W <xiao.w.w...@intel.com>; y...@fridaylinux.org;
> maxime.coque...@redhat.com; Bie, Tiwei <tiwei....@intel.com>
> Cc: dev@dpdk.org; Chen, Junjie J <junjie.j.c...@intel.com>
> Subject: [PATCH v6] vhost: support virtqueue interrupt/notification
> suppression
>
> The driver can suppress interrupt when VIRTIO_F_EVENT_IDX feature bit is
> negotiated. The driver set vring flags to 0, and MAY use used_event in
> available ring to advise device interrupt util reach an index specified
> by used_event. The device ignore the lower bit of vring flags, and send
> an interrupt when index reach used_event.
>
> The device can suppress notification in a manner analogous to the ways
> driver suppress interrupt. The device manipulates flags or avail_event in
> the used ring in the same way the driver manipulates flags or used_event in
> available ring.
>
> This patch is to enable this feature in vhost.
>
> Signed-off-by: Junjie Chen <junjie.j.c...@intel.com>
>
> v6:
> Use volatile qualifier to access avail event idx.
>
> v5:
> Remove updating avail event index in backend.
>
> v2-v4:
> Use definition of VIRTIO_F_EVENT_IDX from kernel.
>
> ---
> lib/librte_vhost/vhost.h | 3 +++
> lib/librte_vhost/virtio_net.c | 46 +++++++++++++++++++++++++++++-------------
> -
> 2 files changed, 34 insertions(+), 15 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 1cc81c1..fc41c20 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -103,6 +103,8 @@ struct vhost_virtqueue {
>
> uint16_t last_avail_idx;
> uint16_t last_used_idx;
> + /* Last used index we notify to front end. */
> + uint16_t signalled_used;
> #define VIRTIO_INVALID_EVENTFD (-1)
> #define VIRTIO_UNINITIALIZED_EVENTFD (-2)
>
> @@ -211,6 +213,7 @@ struct vhost_msg {
> (1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
> (1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
> (1ULL << VIRTIO_RING_F_INDIRECT_DESC) | \
> + (1ULL << VIRTIO_RING_F_EVENT_IDX) | \
> (1ULL << VIRTIO_NET_F_MTU) | \
> (1ULL << VIRTIO_F_IOMMU_PLATFORM))
>
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index 6fee16e..f5777fc 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -52,6 +52,34 @@
>
> #define MAX_BATCH_LEN 256
>
> +#define vhost_used_event(vr) \
> + (*(volatile uint16_t*)&(vr)->avail->ring[(vr)->size])
> +
> +static __rte_always_inline void
> +vhost_notify(struct virtio_net *dev, struct vhost_virtqueue *vq)
> +{
> + /* Don't notify guest if we don't reach index specified by guest. */
> + if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
> + uint16_t old = vq->signalled_used;
> + uint16_t new = vq->last_used_idx;
> +
> + LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d,
> new=%d\n",
> + __func__,
> + vhost_used_event(vq),
> + old, new);
> + if (vring_need_event(vhost_used_event(vq), new, old)
> + && (vq->callfd >= 0)) {
> + vq->signalled_used = vq->last_used_idx;
> + eventfd_write(vq->callfd, (eventfd_t) 1);
> + }
> + } else {
> + /* Kick the guest if necessary. */
> + if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> + && (vq->callfd >= 0))
> + eventfd_write(vq->callfd, (eventfd_t)1);
> + }
> +}
> +
> static bool
> is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t nr_vring)
> {
> @@ -410,11 +438,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t
> queue_id,
>
> /* flush used->idx update before we read avail->flags. */
> rte_mb();
> -
> - /* Kick the guest if necessary. */
> - if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> - && (vq->callfd >= 0))
> - eventfd_write(vq->callfd, (eventfd_t)1);
> + vhost_notify(dev, vq);
> out:
> if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
> vhost_user_iotlb_rd_unlock(vq);
> @@ -704,11 +728,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t
> queue_id,
>
> /* flush used->idx update before we read avail->flags. */
> rte_mb();
> -
> - /* Kick the guest if necessary. */
> - if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> - && (vq->callfd >= 0))
> - eventfd_write(vq->callfd, (eventfd_t)1);
> + vhost_notify(dev, vq);
> }
>
> out:
> @@ -1106,11 +1126,7 @@ update_used_idx(struct virtio_net *dev, struct
> vhost_virtqueue *vq,
> vq->used->idx += count;
> vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
> sizeof(vq->used->idx));
> -
> - /* Kick guest if required. */
> - if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> - && (vq->callfd >= 0))
> - eventfd_write(vq->callfd, (eventfd_t)1);
> + vhost_notify(dev, vq);
> }
>
> static __rte_always_inline struct zcopy_mbuf *
> --
> 2.0.1
Reviewed-by: Xiao Wang <xiao.w.w...@intel.com>
