From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OA7CZAgq" Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8032EB9 for ; Thu, 30 Nov 2023 05:59:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1701352747; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=/uda2OoXWZFrWrKrJB2e3oA9p9YZZZPgmKwHuRaVzhs=; b=OA7CZAgqvHhmGz8jjVQYPhWDNSwPw2HYWvZBj/F2l83Mho10jvPzWBZ6fg0gcWvbrbqUGE /OyRdXYhZ2Qdr4/LKYtxkybNOxcnOpJRPXLoMu4F+T8BgRviqJysAVikDiGf5MXt0cweuF c1NlzR+cOwRThWbDngG3ykS2UaZSjq0= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-235-yqAqr-xhMTyQue2LTBL9rw-1; Thu, 30 Nov 2023 08:59:04 -0500 X-MC-Unique: yqAqr-xhMTyQue2LTBL9rw-1 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-332ee20a3f0so1022156f8f.0 for ; Thu, 30 Nov 2023 05:59:04 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701352743; x=1701957543; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=/uda2OoXWZFrWrKrJB2e3oA9p9YZZZPgmKwHuRaVzhs=; b=DrokLAN9clalho7i9kh+Dkc7WkdHK9wqY22oNJWC8bwR0UrsiTlCIPpgBAnEiJ6rgz z2j5R/A8/bpOrsouGHRBi/3EEq5q9EwaP4NLbQmciMUnXs+qUbL+IjdloJp+wRG6/2Xp G+31KHtI06QW1sHCUgjqZ0suZA4Yly5xc3G7svQWxKDcwlJ9Mscv/SAZn9KqlDFqgwZg KF1icDpX9R7nATHFwowNnxC91rF9/d1ddDs/WfJ5S1RZGzEESg62BncPea7VqSMKU/n0 jFF31YpE3/A34+oD6WU4BLkEmVHRmTYtib+QyaZfB235PbmHOppViAzt7B0JPh+D7jWC YYAA== X-Gm-Message-State: AOJu0Yy/BAkErFG2Z4iG29chMyzPoZRCCdMwRTkrq0EB/1x2EaXe5eyU aZOP6U4Je1fbwPd+KOL5ejmlk4IST4Z1fhNbscTjOGdhiQwi+C+cWJk7qB++DNYvC8xf4YpsG/2 gUfnDv9u2o+NBeOtL X-Received: by 2002:adf:ec83:0:b0:332:ef1e:bb99 with SMTP id z3-20020adfec83000000b00332ef1ebb99mr13949219wrn.26.1701352743402; Thu, 30 Nov 2023 05:59:03 -0800 (PST) X-Google-Smtp-Source: AGHT+IFH4PpTRoBpdxxMudyT8DYADIaNEbwtS9Mz//7m0f6heYFXMJsx86J63u6mQnwoWb4XVKTMIg== X-Received: by 2002:adf:ec83:0:b0:332:ef1e:bb99 with SMTP id z3-20020adfec83000000b00332ef1ebb99mr13949197wrn.26.1701352743025; Thu, 30 Nov 2023 05:59:03 -0800 (PST) Received: from redhat.com ([2.55.10.128]) by smtp.gmail.com with ESMTPSA id m10-20020a5d6a0a000000b00332eb96cb73sm1629406wru.73.2023.11.30.05.59.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Nov 2023 05:59:02 -0800 (PST) Date: Thu, 30 Nov 2023 08:58:58 -0500 From: "Michael S. Tsirkin" To: Arseniy Krasnov Cc: Stefan Hajnoczi , Stefano Garzarella , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jason Wang , Bobby Eshleman , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@sberdevices.ru, oxffffaa@gmail.com Subject: Re: [PATCH net-next v5 2/3] virtio/vsock: send credit update during setting SO_RCVLOWAT Message-ID: <20231130085445-mutt-send-email-mst@kernel.org> References: <20231130130840.253733-1-avkrasnov@salutedevices.com> <20231130130840.253733-3-avkrasnov@salutedevices.com> <20231130084044-mutt-send-email-mst@kernel.org> <02de8982-ec4a-b3b2-e8e5-1bca28cfc01b@salutedevices.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <02de8982-ec4a-b3b2-e8e5-1bca28cfc01b@salutedevices.com> 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 > >> --- > >> 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. > > > > > > >> +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 > >