This commit is the first in a series to add support for packed
virtqueues in vhost_shadow_virtqueue.
This patch implements the insertion of available buffers in the
descriptor area. It takes into account descriptor chains, but does
not consider indirect descriptors.
Also validate svq-specific features that vdpa supports.
Signed-off-by: Sahil Siddiq <sahil...@proton.me>
---
Changes v3 -> v4:
- Split commit #1 in v3 into 2 commits.
- vhost-shadow-virtqueue.c
(vhost_svq_valid_features): Add enums.
hw/virtio/vhost-shadow-virtqueue.c | 83 +++++++++++++++++++++++++++++-
1 file changed, 81 insertions(+), 2 deletions(-)
diff --git a/hw/virtio/vhost-shadow-virtqueue.c
b/hw/virtio/vhost-shadow-virtqueue.c
index bb7cf6d5db..6eee01ab3c 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -33,6 +33,9 @@ bool vhost_svq_valid_features(uint64_t features, Error **errp)
++b) {
switch (b) {
case VIRTIO_F_ANY_LAYOUT:
+ case VIRTIO_F_RING_PACKED:
+ case VIRTIO_F_RING_RESET:
+ case VIRTIO_RING_F_INDIRECT_DESC:
case VIRTIO_RING_F_EVENT_IDX:
continue;
@@ -178,7 +181,78 @@ static void vhost_svq_add_split(VhostShadowVirtqueue *svq,
/* Update the avail index after write the descriptor */
smp_wmb();
avail->idx = cpu_to_le16(svq->shadow_avail_idx);
+}
+/**
+ * Write descriptors to SVQ packed vring
+ *
+ * @svq: The shadow virtqueue
+ * @out_sg: The iovec to the guest
+ * @out_num: Outgoing iovec length
+ * @in_sg: The iovec from the guest
+ * @in_num: Incoming iovec length
+ * @sgs: Cache for hwaddr
+ * @head: Saves current free_head
+ */
+static void vhost_svq_add_packed(VhostShadowVirtqueue *svq,
+ const struct iovec *out_sg, size_t out_num,
+ const struct iovec *in_sg, size_t in_num,
+ hwaddr *sgs, unsigned *head)
+{
+ uint16_t id, curr, i, head_flags = 0;
+ size_t num = out_num + in_num;
+ unsigned n;
+
+ struct vring_packed_desc *descs = svq->vring_packed.vring.desc;
+
+ *head = svq->vring_packed.next_avail_idx;
+ i = *head;
+ id = svq->free_head;
+ curr = id;
+
+ /* Write descriptors to SVQ packed vring */
+ for (n = 0; n < num; n++) {
+ uint16_t flags = cpu_to_le16(svq->vring_packed.avail_used_flags |
+ (n < out_num ? 0 : VRING_DESC_F_WRITE) |
+ (n + 1 == num ? 0 : VRING_DESC_F_NEXT));
+ if (i == *head) {
+ head_flags = flags;
+ } else {
+ descs[i].flags = flags;
+ }
+
+ descs[i].addr = cpu_to_le64(sgs[n]);
+ descs[i].id = id;
+ if (n < out_num) {
+ descs[i].len = cpu_to_le32(out_sg[n].iov_len);
+ } else {
+ descs[i].len = cpu_to_le32(in_sg[n - out_num].iov_len);
+ }
+
+ curr = cpu_to_le16(svq->desc_next[curr]);
+
+ if (++i >= svq->vring_packed.vring.num) {
+ i = 0;
+ svq->vring_packed.avail_used_flags ^=
+ 1 << VRING_PACKED_DESC_F_AVAIL |
+ 1 << VRING_PACKED_DESC_F_USED;
+ }
+ }
+
+ if (i <= *head) {
+ svq->vring_packed.avail_wrap_counter ^= 1;
+ }
+
+ svq->vring_packed.next_avail_idx = i;
+ svq->free_head = curr;
+
+ /*
+ * A driver MUST NOT make the first descriptor in the list
+ * available before all subsequent descriptors comprising
+ * the list are made available.
+ */
+ smp_wmb();
+ svq->vring_packed.vring.desc[*head].flags = head_flags;
}
static void vhost_svq_kick(VhostShadowVirtqueue *svq)
@@ -240,8 +314,13 @@ int vhost_svq_add(VhostShadowVirtqueue *svq, const struct
iovec *out_sg,
return -EINVAL;
}
- vhost_svq_add_split(svq, out_sg, out_num, in_sg,
- in_num, sgs, &qemu_head);
+ if (virtio_vdev_has_feature(svq->vdev, VIRTIO_F_RING_PACKED)) {
+ vhost_svq_add_packed(svq, out_sg, out_num, in_sg,
+ in_num, sgs, &qemu_head);
+ } else {
+ vhost_svq_add_split(svq, out_sg, out_num, in_sg,
+ in_num, sgs, &qemu_head);
+ }
svq->num_free -= ndescs;
svq->desc_state[qemu_head].elem = elem;
--
2.47.0
