Re: [PATCH net-next v8] virtio/vsock: replace virtio_vsock_pkt with sk_buff

Stefano Garzarella
2022-12-15T08:49:01Z

On Thu, Dec 15, 2022 at 04:36:44AM +0000, Bobby Eshleman wrote:
>This commit changes virtio/vsock to use sk_buff instead of
>virtio_vsock_pkt. Beyond better conforming to other net code, using
>sk_buff allows vsock to use sk_buff-dependent features in the future
>(such as sockmap) and improves throughput.
>
>This patch introduces the following performance changes:
>
>Tool/Config: uperf w/ 64 threads, SOCK_STREAM
>Test Runs: 5, mean of results
>Before: commit 95ec6bce2a0b ("Merge branch 'net-ipa-more-endpoints'")
>
>Test: 64KB, g2h
>Before: 21.63 Gb/s
>After: 25.59 Gb/s (+18%)
>
>Test: 16B, g2h
>Before: 11.86 Mb/s
>After: 17.41 Mb/s (+46%)
>
>Test: 64KB, h2g
>Before: 2.15 Gb/s
>After: 3.6 Gb/s (+67%)
>
>Test: 16B, h2g
>Before: 14.38 Mb/s
>After: 18.43 Mb/s (+28%)
>
>Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
>---
>
>Testing: passed vsock_test h2g and g2h
>Note2: net-next is closed, but sending out now in case more comments
>roll in, as discussed here:
>https://lore.kernel.org/all/Y34SoH1nFTXXLWbK@bullseye/
>
>Changes in v8:
>- vhost/vsock: remove unused enum
>- vhost/vsock: use spin_lock_bh() instead of spin_lock()
>- vsock/loopback: use __skb_dequeue instead of skb_dequeue
>
>Changes in v7:
>- use skb_queue_empty() instead of skb_queue_empty_lockless()
>
>Changes in v6:
>- use skb->cb instead of skb->_skb_refdst
>- use lock-free __skb_queue_purge for rx_queue when rx_lock held
>
>Changes in v5:
>- last_skb instead of skb: last_hdr->len = cpu_to_le32(last_skb->len)
>
>Changes in v4:
>- vdso/bits.h -> linux/bits.h
>- add virtio_vsock_alloc_skb() helper
>- virtio/vsock: rename buf_len -> total_len
>- update last_hdr->len
>- fix build_skb() for vsockmon (tested)
>- add queue helpers
>- use spin_{unlock/lock}_bh() instead of spin_lock()/spin_unlock()
>- note: I only ran a few g2h tests to check that this change
> had no perf impact. The above data is still from patch
> v3.
>
>Changes in v3:
>- fix seqpacket bug
>- use zero in vhost_add_used(..., 0) device doesn't write to buffer
>- use xmas tree style declarations
>- vsock_hdr() -> virtio_vsock_hdr() and other include file style fixes
>- no skb merging
>- save space by not using vsock_metadata
>- use _skb_refdst instead of skb buffer space for flags
>- use skb_pull() to keep track of read bytes instead of using an an
> extra variable 'off' in the skb buffer space
>- remove unnecessary sk_allocation assignment
>- do not zero hdr needlessly
>- introduce virtio_transport_skb_len() because skb->len changes now
>- use spin_lock() directly on queue lock instead of sk_buff_head helpers
> which use spin_lock_irqsave() (e.g., skb_dequeue)
>- do not reduce buffer size to be page size divisible
>- Note: the biggest performance change came from loosening the spinlock
> variation and not reducing the buffer size.
>
>Changes in v2:
>- Use alloc_skb() directly instead of sock_alloc_send_pskb() to minimize
> uAPI changes.
>- Do not marshal errors to -ENOMEM for non-virtio implementations.
>- No longer a part of the original series
>- Some code cleanup and refactoring
>- Include performance stats
>
> drivers/vhost/vsock.c | 213 +++++-------
> include/linux/virtio_vsock.h | 126 +++++--
> net/vmw_vsock/virtio_transport.c | 149 +++------
> net/vmw_vsock/virtio_transport_common.c | 422 +++++++++++++-----------
> net/vmw_vsock/vsock_loopback.c | 51 +--
> 5 files changed, 495 insertions(+), 466 deletions(-)
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index 5703775af129..ee0a00432cb1 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -51,8 +51,7 @@ struct vhost_vsock {
> struct hlist_node hash;
>
> struct vhost_work send_pkt_work;
>- spinlock_t send_pkt_list_lock;
>- struct list_head send_pkt_list; /* host->guest pending packets */
>+ struct sk_buff_head send_pkt_queue; /* host->guest pending packets */
>
> atomic_t queued_replies;
>
>@@ -108,40 +107,33 @@ vhost_transport_do_send_pkt(struct vhost_vsock
>*vsock,
> vhost_disable_notify(&vsock->dev, vq);
>
> do {
>- struct virtio_vsock_pkt *pkt;
>+ struct virtio_vsock_hdr *hdr;
>+ size_t iov_len, payload_len;
> struct iov_iter iov_iter;
>+ u32 flags_to_restore = 0;
>+ struct sk_buff *skb;
> unsigned out, in;
> size_t nbytes;
>- size_t iov_len, payload_len;
> int head;
>- u32 flags_to_restore = 0;
>
>- spin_lock_bh(&vsock->send_pkt_list_lock);
>- if (list_empty(&vsock->send_pkt_list)) {
>- spin_unlock_bh(&vsock->send_pkt_list_lock);
>+ spin_lock_bh(&vsock->send_pkt_queue.lock);
>+ skb = __skb_dequeue(&vsock->send_pkt_queue);
>+ spin_unlock_bh(&vsock->send_pkt_queue.lock);

Sorry for coming late, but I just commented in Paolo's reply.
Here I think we can directly use the new virtio_vsock_skb_dequeue().

With that fixed, you can put my R-b:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Below I left a little comment.

>+
>+ if (!skb) {
> vhost_enable_notify(&vsock->dev, vq);
> break;
> }
>
>- pkt = list_first_entry(&vsock->send_pkt_list,
>- struct virtio_vsock_pkt, list);
>- list_del_init(&pkt->list);
>- spin_unlock_bh(&vsock->send_pkt_list_lock);
>-
> head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
> &out, &in, NULL, NULL);
> if (head < 0) {
>- spin_lock_bh(&vsock->send_pkt_list_lock);
>- list_add(&pkt->list, &vsock->send_pkt_list);
>- spin_unlock_bh(&vsock->send_pkt_list_lock);
>+ virtio_vsock_skb_queue_head(&vsock->send_pkt_queue, skb);
> break;
> }
>
> if (head == vq->num) {
>- spin_lock_bh(&vsock->send_pkt_list_lock);
>- list_add(&pkt->list, &vsock->send_pkt_list);
>- spin_unlock_bh(&vsock->send_pkt_list_lock);
>-
>+ virtio_vsock_skb_queue_head(&vsock->send_pkt_queue, skb);
> /* We cannot finish yet if more buffers snuck in while
> * re-enabling notify.
> */
>@@ -153,26 +145,27 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> }
>
> if (out) {
>- virtio_transport_free_pkt(pkt);
>+ kfree_skb(skb);
> vq_err(vq, "Expected 0 output buffers, got %u\n", out);
> break;
> }
>
> iov_len = iov_length(&vq->iov[out], in);
>- if (iov_len < sizeof(pkt->hdr)) {
>- virtio_transport_free_pkt(pkt);
>+ if (iov_len < sizeof(*hdr)) {
>+ kfree_skb(skb);
> vq_err(vq, "Buffer len [%zu] too small\n", iov_len);
> break;
> }
>
> iov_iter_init(&iov_iter, READ, &vq->iov[out], in, iov_len);
>- payload_len = pkt->len - pkt->off;
>+ payload_len = skb->len;
>+ hdr = virtio_vsock_hdr(skb);
>
> /* If the packet is greater than the space available in the
> * buffer, we split it using multiple buffers.
> */
>- if (payload_len > iov_len - sizeof(pkt->hdr)) {
>- payload_len = iov_len - sizeof(pkt->hdr);
>+ if (payload_len > iov_len - sizeof(*hdr)) {
>+ payload_len = iov_len - sizeof(*hdr);
>
> /* As we are copying pieces of large packet's buffer to
> * small rx buffers, headers of packets in rx queue are
>@@ -185,31 +178,30 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> * bits set. After initialized header will be copied to
> * rx buffer, these required bits will be restored.
> */
>- if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOM) {
>- pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
>+ if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) {
>+ hdr->flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
> flags_to_restore |= VIRTIO_VSOCK_SEQ_EOM;
>
>- if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) {
>- pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
>+ if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOR) {
>+ hdr->flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
> flags_to_restore |= VIRTIO_VSOCK_SEQ_EOR;
> }
> }
> }
>
> /* Set the correct length in the header */
>- pkt->hdr.len = cpu_to_le32(payload_len);
>+ hdr->len = cpu_to_le32(payload_len);
>
>- nbytes = copy_to_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
>- if (nbytes != sizeof(pkt->hdr)) {
>- virtio_transport_free_pkt(pkt);
>+ nbytes = copy_to_iter(hdr, sizeof(*hdr), &iov_iter);
>+ if (nbytes != sizeof(*hdr)) {
>+ kfree_skb(skb);
> vq_err(vq, "Faulted on copying pkt hdr\n");
> break;
> }
>
>- nbytes = copy_to_iter(pkt->buf + pkt->off, payload_len,
>- &iov_iter);
>+ nbytes = copy_to_iter(skb->data, payload_len, &iov_iter);
> if (nbytes != payload_len) {
>- virtio_transport_free_pkt(pkt);
>+ kfree_skb(skb);
> vq_err(vq, "Faulted on copying pkt buf\n");
> break;
> }
>@@ -217,31 +209,28 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> /* Deliver to monitoring devices all packets that we
> * will transmit.
> */
>- virtio_transport_deliver_tap_pkt(pkt);
>+ virtio_transport_deliver_tap_pkt(skb);
>
>- vhost_add_used(vq, head, sizeof(pkt->hdr) + payload_len);
>+ vhost_add_used(vq, head, sizeof(*hdr) + payload_len);
> added = true;
>
>- pkt->off += payload_len;
>+ skb_pull(skb, payload_len);
> total_len += payload_len;
>
> /* If we didn't send all the payload we can requeue the packet
> * to send it with the next available buffer.
> */
>- if (pkt->off < pkt->len) {
>- pkt->hdr.flags |= cpu_to_le32(flags_to_restore);
>+ if (skb->len > 0) {
>+ hdr->flags |= cpu_to_le32(flags_to_restore);
>
>- /* We are queueing the same virtio_vsock_pkt to handle
>+ /* We are queueing the same skb to handle
> * the remaining bytes, and we want to deliver it
> * to monitoring devices in the next iteration.
> */
>- pkt->tap_delivered = false;
>-
>- spin_lock_bh(&vsock->send_pkt_list_lock);
>- list_add(&pkt->list, &vsock->send_pkt_list);
>- spin_unlock_bh(&vsock->send_pkt_list_lock);
>+ virtio_vsock_skb_clear_tap_delivered(skb);
>+ virtio_vsock_skb_queue_head(&vsock->send_pkt_queue, skb);
> } else {
>- if (pkt->reply) {
>+ if (virtio_vsock_skb_reply(skb)) {
> int val;
>
> val = atomic_dec_return(&vsock->queued_replies);
>@@ -253,7 +242,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> restart_tx = true;
> }
>
>- virtio_transport_free_pkt(pkt);
>+ consume_skb(skb);
> }
> } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
> if (added)
>@@ -278,28 +267,26 @@ static void vhost_transport_send_pkt_work(struct vhost_work *work)
> }
>
> static int
>-vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
>+vhost_transport_send_pkt(struct sk_buff *skb)
> {
>+ struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
> struct vhost_vsock *vsock;
>- int len = pkt->len;
>+ int len = skb->len;
>
> rcu_read_lock();
>
> /* Find the vhost_vsock according to guest context id */
>- vsock = vhost_vsock_get(le64_to_cpu(pkt->hdr.dst_cid));
>+ vsock = vhost_vsock_get(le64_to_cpu(hdr->dst_cid));
> if (!vsock) {
> rcu_read_unlock();
>- virtio_transport_free_pkt(pkt);
>+ kfree_skb(skb);
> return -ENODEV;
> }
>
>- if (pkt->reply)
>+ if (virtio_vsock_skb_reply(skb))
> atomic_inc(&vsock->queued_replies);
>
>- spin_lock_bh(&vsock->send_pkt_list_lock);
>- list_add_tail(&pkt->list, &vsock->send_pkt_list);
>- spin_unlock_bh(&vsock->send_pkt_list_lock);
>-
>+ virtio_vsock_skb_queue_tail(&vsock->send_pkt_queue, skb);
> vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);
>
> rcu_read_unlock();
>@@ -310,10 +297,8 @@ static int
> vhost_transport_cancel_pkt(struct vsock_sock *vsk)
> {
> struct vhost_vsock *vsock;
>- struct virtio_vsock_pkt *pkt, *n;
> int cnt = 0;
> int ret = -ENODEV;
>- LIST_HEAD(freeme);
>
> rcu_read_lock();
>
>@@ -322,20 +307,7 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk)
> if (!vsock)
> goto out;
>
>- spin_lock_bh(&vsock->send_pkt_list_lock);
>- list_for_each_entry_safe(pkt, n, &vsock->send_pkt_list, list) {
>- if (pkt->vsk != vsk)
>- continue;
>- list_move(&pkt->list, &freeme);
>- }
>- spin_unlock_bh(&vsock->send_pkt_list_lock);
>-
>- list_for_each_entry_safe(pkt, n, &freeme, list) {
>- if (pkt->reply)
>- cnt++;
>- list_del(&pkt->list);
>- virtio_transport_free_pkt(pkt);
>- }
>+ cnt = virtio_transport_purge_skbs(vsk, &vsock->send_pkt_queue);
>
> if (cnt) {
> struct vhost_virtqueue *tx_vq = &vsock->vqs[VSOCK_VQ_TX];
>@@ -352,12 +324,14 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk)
> return ret;
> }
>
>-static struct virtio_vsock_pkt *
>-vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
>+static struct sk_buff *
>+vhost_vsock_alloc_skb(struct vhost_virtqueue *vq,
> unsigned int out, unsigned int in)
> {
>- struct virtio_vsock_pkt *pkt;
>+ struct virtio_vsock_hdr *hdr;
> struct iov_iter iov_iter;
>+ struct sk_buff *skb;
>+ size_t payload_len;
> size_t nbytes;
> size_t len;
>
>@@ -366,50 +340,47 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
> return NULL;
> }
>
>- pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
>- if (!pkt)
>+ len = iov_length(vq->iov, out);
>+
>+ /* len contains both payload and hdr */
>+ skb = virtio_vsock_alloc_skb(len, GFP_KERNEL);
>+ if (!skb)
> return NULL;
>
>- len = iov_length(vq->iov, out);
> iov_iter_init(&iov_iter, WRITE, vq->iov, out, len);
>
>- nbytes = copy_from_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
>- if (nbytes != sizeof(pkt->hdr)) {
>+ hdr = virtio_vsock_hdr(skb);
>+ nbytes = copy_from_iter(hdr, sizeof(*hdr), &iov_iter);
>+ if (nbytes != sizeof(*hdr)) {
> vq_err(vq, "Expected %zu bytes for pkt->hdr, got %zu bytes\n",
>- sizeof(pkt->hdr), nbytes);
>- kfree(pkt);
>+ sizeof(*hdr), nbytes);
>+ kfree_skb(skb);
> return NULL;
> }
>
>- pkt->len = le32_to_cpu(pkt->hdr.len);
>+ payload_len = le32_to_cpu(hdr->len);
>
> /* No payload */
>- if (!pkt->len)
>- return pkt;
>+ if (!payload_len)
>+ return skb;
>
> /* The pkt is too big */
>- if (pkt->len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
>- kfree(pkt);
>+ if (payload_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
>+ kfree_skb(skb);
> return NULL;
> }
>
>- pkt->buf = kvmalloc(pkt->len, GFP_KERNEL);
>- if (!pkt->buf) {
>- kfree(pkt);
>- return NULL;
>- }
>+ virtio_vsock_skb_rx_put(skb);
>
>- pkt->buf_len = pkt->len;
>-
>- nbytes = copy_from_iter(pkt->buf, pkt->len, &iov_iter);
>- if (nbytes != pkt->len) {
>- vq_err(vq, "Expected %u byte payload, got %zu bytes\n",
>- pkt->len, nbytes);
>- virtio_transport_free_pkt(pkt);
>+ nbytes = copy_from_iter(skb->data, payload_len, &iov_iter);
>+ if (nbytes != payload_len) {
>+ vq_err(vq, "Expected %zu byte payload, got %zu bytes\n",
>+ payload_len, nbytes);
>+ kfree_skb(skb);
> return NULL;
> }
>
>- return pkt;
>+ return skb;
> }
>
> /* Is there space left for replies to rx packets? */
>@@ -496,9 +467,9 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> poll.work);
> struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
> dev);
>- struct virtio_vsock_pkt *pkt;
> int head, pkts = 0, total_len = 0;
> unsigned int out, in;
>+ struct sk_buff *skb;
> bool added = false;
>
> mutex_lock(&vq->mutex);
>@@ -511,6 +482,8 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
>
> vhost_disable_notify(&vsock->dev, vq);
> do {
>+ struct virtio_vsock_hdr *hdr;
>+
> if (!vhost_vsock_more_replies(vsock)) {
> /* Stop tx until the device processes already
> * pending replies. Leave tx virtqueue
>@@ -532,24 +505,26 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> break;
> }
>
>- pkt = vhost_vsock_alloc_pkt(vq, out, in);
>- if (!pkt) {
>+ skb = vhost_vsock_alloc_skb(vq, out, in);
>+ if (!skb) {
> vq_err(vq, "Faulted on pkt\n");
> continue;
> }
>
>- total_len += sizeof(pkt->hdr) + pkt->len;
>+ total_len += sizeof(*hdr) + skb->len;
>
> /* Deliver to monitoring devices all received packets */
>- virtio_transport_deliver_tap_pkt(pkt);
>+ virtio_transport_deliver_tap_pkt(skb);
>+
>+ hdr = virtio_vsock_hdr(skb);
>
> /* Only accept correctly addressed packets */
>- if (le64_to_cpu(pkt->hdr.src_cid) == vsock->guest_cid &&
>- le64_to_cpu(pkt->hdr.dst_cid) ==
>+ if (le64_to_cpu(hdr->src_cid) == vsock->guest_cid &&
>+ le64_to_cpu(hdr->dst_cid) ==
> vhost_transport_get_local_cid())
>- virtio_transport_recv_pkt(&vhost_transport, pkt);
>+ virtio_transport_recv_pkt(&vhost_transport, skb);
> else
>- virtio_transport_free_pkt(pkt);
>+ kfree_skb(skb);
>
> vhost_add_used(vq, head, 0);
> added = true;
>@@ -693,8 +668,7 @@ static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
> VHOST_VSOCK_WEIGHT, true, NULL);
>
> file->private_data = vsock;
>- spin_lock_init(&vsock->send_pkt_list_lock);
>- INIT_LIST_HEAD(&vsock->send_pkt_list);
>+ skb_queue_head_init(&vsock->send_pkt_queue);
> vhost_work_init(&vsock->send_pkt_work, vhost_transport_send_pkt_work);
> return 0;
>
>@@ -760,16 +734,7 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
> vhost_vsock_flush(vsock);
> vhost_dev_stop(&vsock->dev);
>
>- spin_lock_bh(&vsock->send_pkt_list_lock);
>- while (!list_empty(&vsock->send_pkt_list)) {
>- struct virtio_vsock_pkt *pkt;
>-
>- pkt = list_first_entry(&vsock->send_pkt_list,
>- struct virtio_vsock_pkt, list);
>- list_del_init(&pkt->list);
>- virtio_transport_free_pkt(pkt);
>- }
>- spin_unlock_bh(&vsock->send_pkt_list_lock);
>+ virtio_vsock_skb_queue_purge(&vsock->send_pkt_queue);
>
> vhost_dev_cleanup(&vsock->dev);
> kfree(vsock->dev.vqs);
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index 35d7eedb5e8e..7ed943615271 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -7,6 +7,106 @@
> #include <net/sock.h>
> #include <net/af_vsock.h>
>
>+#define VIRTIO_VSOCK_SKB_HEADROOM (sizeof(struct virtio_vsock_hdr))
>+
>+struct virtio_vsock_skb_cb {
>+ bool reply;
>+ bool tap_delivered;
>+};
>+
>+#define VIRTIO_VSOCK_SKB_CB(skb) ((struct virtio_vsock_skb_cb *)((skb)->cb))
>+
>+static inline struct virtio_vsock_hdr *virtio_vsock_hdr(struct sk_buff *skb)
>+{
>+ return (struct virtio_vsock_hdr *)skb->head;
>+}
>+
>+static inline bool virtio_vsock_skb_reply(struct sk_buff *skb)
>+{
>+ return VIRTIO_VSOCK_SKB_CB(skb)->reply;
>+}
>+
>+static inline void virtio_vsock_skb_set_reply(struct sk_buff *skb)
>+{
>+ VIRTIO_VSOCK_SKB_CB(skb)->reply = true;
>+}
>+
>+static inline bool virtio_vsock_skb_tap_delivered(struct sk_buff *skb)
>+{
>+ return VIRTIO_VSOCK_SKB_CB(skb)->tap_delivered;
>+}
>+
>+static inline void virtio_vsock_skb_set_tap_delivered(struct sk_buff *skb)
>+{
>+ VIRTIO_VSOCK_SKB_CB(skb)->tap_delivered = true;
>+}
>+
>+static inline void virtio_vsock_skb_clear_tap_delivered(struct sk_buff *skb)
>+{
>+ VIRTIO_VSOCK_SKB_CB(skb)->tap_delivered = false;
>+}

Maybe, we can have a single

virtio_vsock_skb_set_tap_delivered(struct sk_buff *skb,
bool tap_delivered)

to be used in both cases.

Anyway, I don't have a strong opinion on that.

Thanks,
Stefano