On 30.11.2023 16:58, Michael S. Tsirkin wrote: > On Thu, Nov 30, 2023 at 04:43:34PM +0300, Arseniy Krasnov wrote: >> >> >> On 30.11.2023 16:42, Michael S. Tsirkin wrote: >>> On Thu, Nov 30, 2023 at 04:08:39PM +0300, Arseniy Krasnov wrote: >>>> Send credit update message when SO_RCVLOWAT is updated and it is bigger >>>> than number of bytes in rx queue. It is needed, because 'poll()' will >>>> wait until number of bytes in rx queue will be not smaller than >>>> SO_RCVLOWAT, so kick sender to send more data. Otherwise mutual hungup >>>> for tx/rx is possible: sender waits for free space and receiver is >>>> waiting data in 'poll()'. >>>> >>>> Signed-off-by: Arseniy Krasnov <avkrasnov@xxxxxxxxxxxxxxxxx> >>>> --- >>>> Changelog: >>>> v1 -> v2: >>>> * Update commit message by removing 'This patch adds XXX' manner. >>>> * Do not initialize 'send_update' variable - set it directly during >>>> first usage. >>>> v3 -> v4: >>>> * Fit comment in 'virtio_transport_notify_set_rcvlowat()' to 80 chars. >>>> v4 -> v5: >>>> * Do not change callbacks order in transport structures. >>>> >>>> drivers/vhost/vsock.c | 1 + >>>> include/linux/virtio_vsock.h | 1 + >>>> net/vmw_vsock/virtio_transport.c | 1 + >>>> net/vmw_vsock/virtio_transport_common.c | 27 +++++++++++++++++++++++++ >>>> net/vmw_vsock/vsock_loopback.c | 1 + >>>> 5 files changed, 31 insertions(+) >>>> >>>> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c >>>> index f75731396b7e..4146f80db8ac 100644 >>>> --- a/drivers/vhost/vsock.c >>>> +++ b/drivers/vhost/vsock.c >>>> @@ -451,6 +451,7 @@ static struct virtio_transport vhost_transport = { >>>> .notify_buffer_size = virtio_transport_notify_buffer_size, >>>> >>>> .read_skb = virtio_transport_read_skb, >>>> + .notify_set_rcvlowat = virtio_transport_notify_set_rcvlowat >>>> }, >>>> >>>> .send_pkt = vhost_transport_send_pkt, >>>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h >>>> index ebb3ce63d64d..c82089dee0c8 100644 >>>> --- a/include/linux/virtio_vsock.h >>>> +++ b/include/linux/virtio_vsock.h >>>> @@ -256,4 +256,5 @@ void virtio_transport_put_credit(struct virtio_vsock_sock *vvs, u32 credit); >>>> void virtio_transport_deliver_tap_pkt(struct sk_buff *skb); >>>> int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *list); >>>> int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t read_actor); >>>> +int virtio_transport_notify_set_rcvlowat(struct vsock_sock *vsk, int val); >>>> #endif /* _LINUX_VIRTIO_VSOCK_H */ >>>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c >>>> index af5bab1acee1..8007593a3a93 100644 >>>> --- a/net/vmw_vsock/virtio_transport.c >>>> +++ b/net/vmw_vsock/virtio_transport.c >>>> @@ -539,6 +539,7 @@ static struct virtio_transport virtio_transport = { >>>> .notify_buffer_size = virtio_transport_notify_buffer_size, >>>> >>>> .read_skb = virtio_transport_read_skb, >>>> + .notify_set_rcvlowat = virtio_transport_notify_set_rcvlowat >>>> }, >>>> >>>> .send_pkt = virtio_transport_send_pkt, >>>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >>>> index f6dc896bf44c..1cb556ad4597 100644 >>>> --- a/net/vmw_vsock/virtio_transport_common.c >>>> +++ b/net/vmw_vsock/virtio_transport_common.c >>>> @@ -1684,6 +1684,33 @@ int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_acto >>>> } >>>> EXPORT_SYMBOL_GPL(virtio_transport_read_skb); >>>> >>>> +int virtio_transport_notify_set_rcvlowat(struct vsock_sock *vsk, int val) >>>> +{ >>>> + struct virtio_vsock_sock *vvs = vsk->trans; >>>> + bool send_update; >>>> + >>>> + spin_lock_bh(&vvs->rx_lock); >>>> + >>>> + /* If number of available bytes is less than new SO_RCVLOWAT value, >>>> + * kick sender to send more data, because sender may sleep in its >>>> + * 'send()' syscall waiting for enough space at our side. >>>> + */ >>>> + send_update = vvs->rx_bytes < val; >>>> + >>>> + spin_unlock_bh(&vvs->rx_lock); >>>> + >>>> + if (send_update) { >>>> + int err; >>>> + >>>> + err = virtio_transport_send_credit_update(vsk); >>>> + if (err < 0) >>>> + return err; >>>> + } >>>> + >>>> + return 0; >>>> +} >>> >>> >>> I find it strange that this will send a credit update >>> even if nothing changed since this was called previously. >>> I'm not sure whether this is a problem protocol-wise, >>> but it certainly was not envisioned when the protocol was >>> built. WDYT? >> >> >From virtio spec I found: >> >> It is also valid to send a VIRTIO_VSOCK_OP_CREDIT_UPDATE packet without previously receiving a >> VIRTIO_VSOCK_OP_CREDIT_REQUEST packet. This allows communicating updates any time a change >> in buffer space occurs. >> So I guess there is no limitations to send such type of packet, e.g. it is not >> required to be a reply for some another packet. Please, correct me if im wrong. >> >> Thanks, Arseniy > > > Absolutely. My point was different - with this patch it is possible > that you are not adding any credits at all since the previous > VIRTIO_VSOCK_OP_CREDIT_UPDATE. I see, @Stefano, what do you think ? Thanks, Arseniy > >> >>> >>> >>>> +EXPORT_SYMBOL_GPL(virtio_transport_notify_set_rcvlowat); >>>> + >>>> MODULE_LICENSE("GPL v2"); >>>> MODULE_AUTHOR("Asias He"); >>>> MODULE_DESCRIPTION("common code for virtio vsock"); >>>> diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c >>>> index 048640167411..9f4b814fbbc7 100644 >>>> --- a/net/vmw_vsock/vsock_loopback.c >>>> +++ b/net/vmw_vsock/vsock_loopback.c >>>> @@ -98,6 +98,7 @@ static struct virtio_transport loopback_transport = { >>>> .notify_buffer_size = virtio_transport_notify_buffer_size, >>>> >>>> .read_skb = virtio_transport_read_skb, >>>> + .notify_set_rcvlowat = virtio_transport_notify_set_rcvlowat >>>> }, >>>> >>>> .send_pkt = vsock_loopback_send_pkt, >>>> -- >>>> 2.25.1 >>> >