Add VIRTIO_F_IN_ORDER feature support for virtqueue_flush operations.
The goal of the virtqueue_flush operation when the VIRTIO_F_IN_ORDER
feature has been negotiated is to write elements to the used/descriptor
ring in-order and then update used_idx.
The function iterates through the VirtQueueElement used_elems array
in-order starting at vq->used_idx. If the element is valid (filled), the
element is written to the used/descriptor ring. This process continues
until we find an invalid (not filled) element.
If any elements were written, the used_idx is updated.
Signed-off-by: Jonah Palmer <jonah.pal...@oracle.com>
---
hw/virtio/virtio.c | 75 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 74 insertions(+), 1 deletion(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 0730f26f74..13451d0cae 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -997,6 +997,77 @@ static void virtqueue_packed_flush(VirtQueue *vq, unsigned
int count)
}
}
+static void virtqueue_ordered_flush(VirtQueue *vq)
+{
+ unsigned int i = vq->used_idx;
+ unsigned int ndescs = 0;
+ uint16_t old = vq->used_idx;
+ bool packed;
+ VRingUsedElem uelem;
+
+ packed = virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED);
+
+ if (packed) {
+ if (unlikely(!vq->vring.desc)) {
+ return;
+ }
+ } else if (unlikely(!vq->vring.used)) {
+ return;
+ }
+
+ /* First expected in-order element isn't ready, nothing to do */
+ if (!vq->used_elems[i].filled) {
+ return;
+ }
+
+ /* Write first expected in-order element to used ring (split VQs) */
+ if (!packed) {
+ uelem.id = vq->used_elems[i].index;
+ uelem.len = vq->used_elems[i].len;
+ vring_used_write(vq, &uelem, i);
+ }
+
+ ndescs += vq->used_elems[i].ndescs;
+ i += ndescs;
+ if (i >= vq->vring.num) {
+ i -= vq->vring.num;
+ }
+
+ /* Search for more filled elements in-order */
+ while (vq->used_elems[i].filled) {
+ if (packed) {
+ virtqueue_packed_fill_desc(vq, &vq->used_elems[i], ndescs, false);
+ } else {
+ uelem.id = vq->used_elems[i].index;
+ uelem.len = vq->used_elems[i].len;
+ vring_used_write(vq, &uelem, i);
+ }
+
+ vq->used_elems[i].filled = false;
+ ndescs += vq->used_elems[i].ndescs;
+ i += ndescs;
+ if (i >= vq->vring.num) {
+ i -= vq->vring.num;
+ }
+ }
+
+ if (packed) {
+ virtqueue_packed_fill_desc(vq, &vq->used_elems[vq->used_idx], 0, true);
+ vq->used_idx += ndescs;
+ if (vq->used_idx >= vq->vring.num) {
+ vq->used_idx -= vq->vring.num;
+ vq->used_wrap_counter ^= 1;
+ vq->signalled_used_valid = false;
+ }
+ } else {
+ vring_used_idx_set(vq, i);
+ if (unlikely((int16_t)(i - vq->signalled_used) < (uint16_t)(i - old)))
{
+ vq->signalled_used_valid = false;
+ }
+ }
+ vq->inuse -= ndescs;
+}
+
void virtqueue_flush(VirtQueue *vq, unsigned int count)
{
if (virtio_device_disabled(vq->vdev)) {
@@ -1004,7 +1075,9 @@ void virtqueue_flush(VirtQueue *vq, unsigned int count)
return;
}
- if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
+ if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_IN_ORDER)) {
+ virtqueue_ordered_flush(vq);
+ } else if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
virtqueue_packed_flush(vq, count);
} else {
virtqueue_split_flush(vq, count);
--
2.39.3
