Messages in this thread | | | Subject | Re: [RFC v4 4/5] virtio_ring: add event idx support in packed ring | From | Jason Wang <> | Date | Wed, 16 May 2018 21:31:23 +0800 |
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On 2018年05月16日 20:58, Tiwei Bie wrote: > On Wed, May 16, 2018 at 08:17:21PM +0800, Jason Wang wrote: >> On 2018年05月16日 16:37, Tiwei Bie wrote: > [...] >>> @@ -1160,15 +1186,27 @@ static void virtqueue_disable_cb_packed(struct virtqueue *_vq) >>> static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq) >>> { >>> struct vring_virtqueue *vq = to_vvq(_vq); >>> + u16 wrap_counter; >>> START_USE(vq); >>> /* We optimistically turn back on interrupts, then check if there was >>> * more to do. */ >>> + /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to >>> + * either clear the flags bit or point the event index at the next >>> + * entry. Always update the event index to keep code simple. */ >>> + >>> + wrap_counter = vq->wrap_counter; >>> + if (vq->last_used_idx > vq->next_avail_idx) >> Should this be ">=" consider rx refill may try to completely fill the ring? > It seems that there are two cases that last_used_idx > equals to next_avail_idx. The first one is that the > ring is empty. And the second one is that the ring > is full. Although in the first case, most probably, > the driver won't enable the interrupt. > > Maybe I really should track the used_wrap_counter > instead of calculating it each time I need it.. I'll > give it a try.. >
Right, good to know and this will match spec sample code.
Thanks
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