Re: [PATCH v10 15/18] vhost/vsock: support SEQPACKET for transport

From: Stefano Garzarella
Date: Thu Jun 03 2021 - 11:35:10 EST


On Thu, May 20, 2021 at 10:19:13PM +0300, Arseny Krasnov wrote:

Please describe better the changes included in this patch in the first part of the commit message.

As vhost places data in buffers of guest's rx queue, keep SEQ_EOR
bit set only when last piece of data is copied. Otherwise we get
sequence packets for one socket in guest's rx queue with SEQ_EOR bit
set. Also remove ignore of non-stream type of packets, handle SEQPACKET
feature bit.

Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
---
v9 -> v10:
1) Move 'restore_flag' handling to 'payload_len' calculation
block.

drivers/vhost/vsock.c | 44 +++++++++++++++++++++++++++++++++++++++----
1 file changed, 40 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 5e78fb719602..63d15beaad05 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -31,7 +31,8 @@

enum {
VHOST_VSOCK_FEATURES = VHOST_FEATURES |
- (1ULL << VIRTIO_F_ACCESS_PLATFORM)
+ (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
+ (1ULL << VIRTIO_VSOCK_F_SEQPACKET)
};

enum {
@@ -56,6 +57,7 @@ struct vhost_vsock {
atomic_t queued_replies;

u32 guest_cid;
+ bool seqpacket_allow;
};

static u32 vhost_transport_get_local_cid(void)
@@ -112,6 +114,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
size_t nbytes;
size_t iov_len, payload_len;
int head;
+ bool restore_flag = false;

spin_lock_bh(&vsock->send_pkt_list_lock);
if (list_empty(&vsock->send_pkt_list)) {
@@ -168,9 +171,15 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
/* 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))
+ if (payload_len > iov_len - sizeof(pkt->hdr)) {
payload_len = iov_len - sizeof(pkt->hdr);


Please, add a comment here to explain why we need this.

+ if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) {
+ pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
+ restore_flag = true;
+ }
+ }
+
/* Set the correct length in the header */
pkt->hdr.len = cpu_to_le32(payload_len);

@@ -181,6 +190,9 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
break;
}

+ if (restore_flag)
+ pkt->hdr.flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
+

Maybe we can restore the flag only if we are queueing again the same packet, I mean in the `if (pkt->off < pkt->len) {` branch below.

What do you think?

nbytes = copy_to_iter(pkt->buf + pkt->off, payload_len,
&iov_iter);
if (nbytes != payload_len) {
@@ -354,8 +366,7 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
return NULL;
}

- if (le16_to_cpu(pkt->hdr.type) == VIRTIO_VSOCK_TYPE_STREAM)
- pkt->len = le32_to_cpu(pkt->hdr.len);
+ pkt->len = le32_to_cpu(pkt->hdr.len);

/* No payload */
if (!pkt->len)
@@ -398,6 +409,8 @@ static bool vhost_vsock_more_replies(struct vhost_vsock *vsock)
return val < vq->num;
}

+static bool vhost_transport_seqpacket_allow(u32 remote_cid);
+
static struct virtio_transport vhost_transport = {
.transport = {
.module = THIS_MODULE,
@@ -424,6 +437,10 @@ static struct virtio_transport vhost_transport = {
.stream_is_active = virtio_transport_stream_is_active,
.stream_allow = virtio_transport_stream_allow,

+ .seqpacket_dequeue = virtio_transport_seqpacket_dequeue,
+ .seqpacket_enqueue = virtio_transport_seqpacket_enqueue,
+ .seqpacket_allow = vhost_transport_seqpacket_allow,
+
.notify_poll_in = virtio_transport_notify_poll_in,
.notify_poll_out = virtio_transport_notify_poll_out,
.notify_recv_init = virtio_transport_notify_recv_init,
@@ -441,6 +458,22 @@ static struct virtio_transport vhost_transport = {
.send_pkt = vhost_transport_send_pkt,
};

+static bool vhost_transport_seqpacket_allow(u32 remote_cid)
+{
+ struct vhost_vsock *vsock;
+ bool seqpacket_allow = false;
+
+ rcu_read_lock();
+ vsock = vhost_vsock_get(remote_cid);
+
+ if (vsock)
+ seqpacket_allow = vsock->seqpacket_allow;
+
+ rcu_read_unlock();
+
+ return seqpacket_allow;
+}
+
static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
{
struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
@@ -785,6 +818,9 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
goto err;
}

+ if (features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET))
+ vsock->seqpacket_allow = true;
+
for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
vq = &vsock->vqs[i];
mutex_lock(&vq->mutex);
--
2.25.1