On Thu, Mar 28, 2024 at 5:22 PM Jonah Palmer <jonah.pal...@oracle.com> wrote: > > Initialize sequence variables for VirtQueue and VirtQueueElement > structures. A VirtQueue's sequence variables are initialized when a > VirtQueue is being created or reset. A VirtQueueElement's sequence > variable is initialized when a VirtQueueElement is being initialized. > These variables will be used to support the VIRTIO_F_IN_ORDER feature. > > A VirtQueue's used_seq_idx represents the next expected index in a > sequence of VirtQueueElements to be processed (put on the used ring). > The next VirtQueueElement added to the used ring must match this > sequence number before additional elements can be safely added to the > used ring. It's also particularly useful for helping find the number of > new elements added to the used ring. > > A VirtQueue's current_seq_idx represents the current sequence index. > This value is essentially a counter where the value is assigned to a new > VirtQueueElement and then incremented. Given its uint16_t type, this > sequence number can be between 0 and 65,535. > > A VirtQueueElement's seq_idx represents the sequence number assigned to > the VirtQueueElement when it was created. This value must match with the > VirtQueue's used_seq_idx before the element can be put on the used ring > by the device. > > Signed-off-by: Jonah Palmer <jonah.pal...@oracle.com> > --- > hw/virtio/virtio.c | 18 ++++++++++++++++++ > include/hw/virtio/virtio.h | 1 + > 2 files changed, 19 insertions(+) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index fb6b4ccd83..069d96df99 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -132,6 +132,10 @@ struct VirtQueue > uint16_t used_idx; > bool used_wrap_counter; > > + /* In-Order sequence indices */ > + uint16_t used_seq_idx; > + uint16_t current_seq_idx; > +
I'm having a hard time understanding the difference between these and last_avail_idx and used_idx. It seems to me if we replace them everything will work? What am I missing? > /* Last used index value we have signalled on */ > uint16_t signalled_used; > > @@ -1621,6 +1625,11 @@ static void *virtqueue_split_pop(VirtQueue *vq, size_t > sz) > elem->in_sg[i] = iov[out_num + i]; > } > > + /* Assign sequence index for in-order processing */ > + if (virtio_vdev_has_feature(vdev, VIRTIO_F_IN_ORDER)) { > + elem->seq_idx = vq->current_seq_idx++; > + } > + > vq->inuse++; > > trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num); > @@ -1760,6 +1769,11 @@ static void *virtqueue_packed_pop(VirtQueue *vq, > size_t sz) > vq->shadow_avail_idx = vq->last_avail_idx; > vq->shadow_avail_wrap_counter = vq->last_avail_wrap_counter; > > + /* Assign sequence index for in-order processing */ > + if (virtio_vdev_has_feature(vdev, VIRTIO_F_IN_ORDER)) { > + elem->seq_idx = vq->current_seq_idx++; > + } > + > trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num); > done: > address_space_cache_destroy(&indirect_desc_cache); > @@ -2087,6 +2101,8 @@ static void __virtio_queue_reset(VirtIODevice *vdev, > uint32_t i) > vdev->vq[i].notification = true; > vdev->vq[i].vring.num = vdev->vq[i].vring.num_default; > vdev->vq[i].inuse = 0; > + vdev->vq[i].used_seq_idx = 0; > + vdev->vq[i].current_seq_idx = 0; > virtio_virtqueue_reset_region_cache(&vdev->vq[i]); > } > > @@ -2334,6 +2350,8 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int > queue_size, > vdev->vq[i].vring.align = VIRTIO_PCI_VRING_ALIGN; > vdev->vq[i].handle_output = handle_output; > vdev->vq[i].used_elems = g_new0(VirtQueueElement, queue_size); > + vdev->vq[i].used_seq_idx = 0; > + vdev->vq[i].current_seq_idx = 0; > > return &vdev->vq[i]; > } > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > index b3c74a1bca..910b2a3427 100644 > --- a/include/hw/virtio/virtio.h > +++ b/include/hw/virtio/virtio.h > @@ -75,6 +75,7 @@ typedef struct VirtQueueElement > hwaddr *out_addr; > struct iovec *in_sg; > struct iovec *out_sg; > + uint16_t seq_idx; > } VirtQueueElement; > > #define VIRTIO_QUEUE_MAX 1024 > -- > 2.39.3 >