On Thu, 1 Sep 2022 13:54:33 +0800, Guo Zhi <[email protected]> wrote: > If in order feature negotiated, we can skip the used ring to get > buffer's desc id sequentially. For skipped buffers in the batch, the > used ring doesn't contain the buffer length, actually there is not need > to get skipped buffers' length as they are tx buffer.
As far as I know, currently virtio-net will use the buffer's length here for statistics. So whether virtio-net also needs to make some changes. Thanks. > > Signed-off-by: Guo Zhi <[email protected]> > --- > drivers/virtio/virtio_ring.c | 74 +++++++++++++++++++++++++++++++----- > 1 file changed, 64 insertions(+), 10 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 00aa4b7a49c2..d52624179b43 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -103,6 +103,9 @@ struct vring_virtqueue { > /* Host supports indirect buffers */ > bool indirect; > > + /* Host supports in order feature */ > + bool in_order; > + > /* Host publishes avail event idx */ > bool event; > > @@ -144,6 +147,19 @@ struct vring_virtqueue { > /* DMA address and size information */ > dma_addr_t queue_dma_addr; > size_t queue_size_in_bytes; > + > + /* If in_order feature is negotiated, here is the next > head to consume */ > + u16 next_desc_begin; > + /* > + * If in_order feature is negotiated, > + * here is the last descriptor's id in the batch > + */ > + u16 last_desc_in_batch; > + /* > + * If in_order feature is negotiated, > + * buffers except last buffer in the batch are skipped > buffer > + */ > + bool is_skipped_buffer; > } split; > > /* Available for packed ring */ > @@ -584,8 +600,6 @@ static inline int virtqueue_add_split(struct virtqueue > *_vq, > total_sg * sizeof(struct vring_desc), > VRING_DESC_F_INDIRECT, > false); > - vq->split.desc_extra[head & (vq->split.vring.num - 1)].flags &= > - ~VRING_DESC_F_NEXT; > } > > /* We're using some buffers from the free list. */ > @@ -701,8 +715,16 @@ static void detach_buf_split(struct vring_virtqueue *vq, > unsigned int head, > } > > vring_unmap_one_split(vq, i); > - vq->split.desc_extra[i].next = vq->free_head; > - vq->free_head = head; > + /* > + * If in_order feature is negotiated, > + * the descriptors are made available in order. > + * Since the free_head is already a circular list, > + * it must consume it sequentially. > + */ > + if (!vq->in_order) { > + vq->split.desc_extra[i].next = vq->free_head; > + vq->free_head = head; > + } > > /* Plus final descriptor */ > vq->vq.num_free++; > @@ -744,7 +766,7 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue > *_vq, > { > struct vring_virtqueue *vq = to_vvq(_vq); > void *ret; > - unsigned int i; > + unsigned int i, j; > u16 last_used; > > START_USE(vq); > @@ -763,11 +785,38 @@ static void *virtqueue_get_buf_ctx_split(struct > virtqueue *_vq, > /* Only get used array entries after they have been exposed by host. */ > virtio_rmb(vq->weak_barriers); > > - last_used = (vq->last_used_idx & (vq->split.vring.num - 1)); > - i = virtio32_to_cpu(_vq->vdev, > - vq->split.vring.used->ring[last_used].id); > - *len = virtio32_to_cpu(_vq->vdev, > - vq->split.vring.used->ring[last_used].len); > + if (vq->in_order) { > + last_used = (vq->last_used_idx & (vq->split.vring.num - 1)); > + if (!vq->split.is_skipped_buffer) { > + vq->split.last_desc_in_batch = > + virtio32_to_cpu(_vq->vdev, > + > vq->split.vring.used->ring[last_used].id); > + vq->split.is_skipped_buffer = true; > + } > + /* For skipped buffers in batch, we can ignore the len info, > simply set len as 0 */ > + if (vq->split.next_desc_begin != vq->split.last_desc_in_batch) { > + *len = 0; > + } else { > + *len = virtio32_to_cpu(_vq->vdev, > + > vq->split.vring.used->ring[last_used].len); > + vq->split.is_skipped_buffer = false; > + } > + i = vq->split.next_desc_begin; > + j = i; > + /* Indirect only takes one descriptor in descriptor table */ > + while (!vq->indirect && (vq->split.desc_extra[j].flags & > VRING_DESC_F_NEXT)) > + j = (j + 1) & (vq->split.vring.num - 1); > + /* move to next */ > + j = (j + 1) % vq->split.vring.num; > + /* Next buffer will use this descriptor in order */ > + vq->split.next_desc_begin = j; > + } else { > + last_used = (vq->last_used_idx & (vq->split.vring.num - 1)); > + i = virtio32_to_cpu(_vq->vdev, > + vq->split.vring.used->ring[last_used].id); > + *len = virtio32_to_cpu(_vq->vdev, > + > vq->split.vring.used->ring[last_used].len); > + } > > if (unlikely(i >= vq->split.vring.num)) { > BAD_RING(vq, "id %u out of range\n", i); > @@ -2223,6 +2272,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int > index, > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > !context; > + vq->in_order = virtio_has_feature(vdev, VIRTIO_F_IN_ORDER); > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > > if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > @@ -2235,6 +2285,10 @@ struct virtqueue *__vring_new_virtqueue(unsigned int > index, > vq->split.avail_flags_shadow = 0; > vq->split.avail_idx_shadow = 0; > > + vq->split.next_desc_begin = 0; > + vq->split.last_desc_in_batch = 0; > + vq->split.is_skipped_buffer = false; > + > /* No callback? Tell other side not to bother us. */ > if (!callback) { > vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT; > -- > 2.17.1 > _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
