From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DADCDC47082 for ; Tue, 8 Jun 2021 10:25:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C369160FE5 for ; Tue, 8 Jun 2021 10:25:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230351AbhFHK1X (ORCPT ); Tue, 8 Jun 2021 06:27:23 -0400 Received: from mx13.kaspersky-labs.com ([91.103.66.164]:20063 "EHLO mx13.kaspersky-labs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229626AbhFHK1U (ORCPT ); Tue, 8 Jun 2021 06:27:20 -0400 Received: from relay13.kaspersky-labs.com (unknown [127.0.0.10]) by relay13.kaspersky-labs.com (Postfix) with ESMTP id E6A8B520CC4; Tue, 8 Jun 2021 13:25:01 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kaspersky.com; s=mail202102; t=1623147902; bh=La5ekusN6xEqDTr0cwyUT5a093FNCxQm8tgZbiSUiBs=; h=Subject:To:From:Message-ID:Date:MIME-Version:Content-Type; b=xHtTW1VvvowRh9bmNIoA703wMOPaTlLHutBzIcdrCtw90UVgu8Xh/2ImAO6lHL6w7 tfhSFGpN42KvtDaW5SFKXYL0Obgh7cHxKTE28XpsdeAnH6IWZTynQO94HJUut5UD9p kA+ndeRgQRS5zaFMJi1B7EqOkZdAbpce6vZBX4NXDF3fG7xyg9l7V9IS/hqLX+cvZY Nad1vw8rc3rm/5FWtBRrBgtNveDCb48HTBxwDT6YvanDoWPoqDRsjTn42UXAo0GlE5 M/MAjmMj8BJPgDmw8XQszNS67iVFbYi/S5bVcAgZEtVqp3r6UMXuJ3wWQ+ph7taBkH MCi1knSarpGQQ== Received: from mail-hq2.kaspersky.com (unknown [91.103.66.206]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (Client CN "mail-hq2.kaspersky.com", Issuer "Kaspersky MailRelays CA G3" (verified OK)) by mailhub13.kaspersky-labs.com (Postfix) with ESMTPS id 1C379520CC2; Tue, 8 Jun 2021 13:25:01 +0300 (MSK) Received: from [10.16.171.77] (10.64.68.128) by hqmailmbx3.avp.ru (10.64.67.243) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.14; Tue, 8 Jun 2021 13:25:00 +0300 Subject: Re: [PATCH v10 11/18] virtio/vsock: dequeue callback for SOCK_SEQPACKET To: Stefano Garzarella CC: Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jorgen Hansen , Norbert Slusarek , Colin Ian King , Andra Paraschiv , "kvm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "oxffffaa@gmail.com" References: <20210520191357.1270473-1-arseny.krasnov@kaspersky.com> <20210520191801.1272027-1-arseny.krasnov@kaspersky.com> <20210603144513.ryjzauq7abnjogu3@steredhat> <6b833ccf-ea93-db6a-4743-463ac1cfe817@kaspersky.com> <20210604150324.winiikx5h3p6gsyy@steredhat> <20210607110421.wkx4dj7wipwsqztj@steredhat> <8e2eb802-7c5d-70b0-82b5-ec8de4fdc046@kaspersky.com> <20210608082320.vs2tzgpxgr2dhxye@steredhat> <3c35f04a-8406-d26f-27d0-becbd3c43c1b@kaspersky.com> <20210608101952.6meiasy7zqp474sf@steredhat> From: Arseny Krasnov Message-ID: <8ca7fe68-81b7-8984-bf0f-db2384985988@kaspersky.com> Date: Tue, 8 Jun 2021 13:24:58 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210608101952.6meiasy7zqp474sf@steredhat> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.64.68.128] X-ClientProxiedBy: hqmailmbx1.avp.ru (10.64.67.241) To hqmailmbx3.avp.ru (10.64.67.243) X-KSE-ServerInfo: hqmailmbx3.avp.ru, 9 X-KSE-AntiSpam-Interceptor-Info: scan successful X-KSE-AntiSpam-Version: 5.9.20, Database issued on: 06/08/2021 10:07:38 X-KSE-AntiSpam-Status: KAS_STATUS_NOT_DETECTED X-KSE-AntiSpam-Method: none X-KSE-AntiSpam-Rate: 0 X-KSE-AntiSpam-Info: Lua profiles 164175 [Jun 08 2021] X-KSE-AntiSpam-Info: Version: 5.9.20.0 X-KSE-AntiSpam-Info: Envelope from: arseny.krasnov@kaspersky.com X-KSE-AntiSpam-Info: LuaCore: 448 448 71fb1b37213ce9a885768d4012c46ac449c77b17 X-KSE-AntiSpam-Info: {Tracking_phishing_log_reg_60_70} X-KSE-AntiSpam-Info: {Tracking_from_domain_doesnt_match_to} X-KSE-AntiSpam-Info: d41d8cd98f00b204e9800998ecf8427e.com:7.1.1;127.0.0.199:7.1.2;kaspersky.com:7.1.1 X-KSE-AntiSpam-Info: Rate: 0 X-KSE-AntiSpam-Info: Status: not_detected X-KSE-AntiSpam-Info: Method: none X-KSE-Antiphishing-Info: Clean X-KSE-Antiphishing-ScanningType: Deterministic X-KSE-Antiphishing-Method: None X-KSE-Antiphishing-Bases: 06/08/2021 10:09:00 X-KSE-AttachmentFiltering-Interceptor-Info: no applicable attachment filtering rules found X-KSE-Antivirus-Interceptor-Info: scan successful X-KSE-Antivirus-Info: Clean, bases: 08.06.2021 9:07:00 X-KSE-BulkMessagesFiltering-Scan-Result: InTheLimit X-KSE-AttachmentFiltering-Interceptor-Info: no applicable attachment filtering rules found X-KSE-BulkMessagesFiltering-Scan-Result: InTheLimit X-KLMS-Rule-ID: 52 X-KLMS-Message-Action: clean X-KLMS-AntiSpam-Status: not scanned, disabled by settings X-KLMS-AntiSpam-Interceptor-Info: not scanned X-KLMS-AntiPhishing: Clean, bases: 2021/06/08 07:53:00 X-KLMS-AntiVirus: Kaspersky Security for Linux Mail Server, version 8.0.3.30, bases: 2021/06/08 08:56:00 #16686208 X-KLMS-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 08.06.2021 13:19, Stefano Garzarella wrote: > On Tue, Jun 08, 2021 at 12:40:39PM +0300, Arseny Krasnov wrote: >> On 08.06.2021 11:23, Stefano Garzarella wrote: >>> On Mon, Jun 07, 2021 at 04:18:38PM +0300, Arseny Krasnov wrote: >>>> On 07.06.2021 14:04, Stefano Garzarella wrote: >>>>> On Fri, Jun 04, 2021 at 09:03:26PM +0300, Arseny Krasnov wrote: >>>>>> On 04.06.2021 18:03, Stefano Garzarella wrote: >>>>>>> On Fri, Jun 04, 2021 at 04:12:23PM +0300, Arseny Krasnov wrote: >>>>>>>> On 03.06.2021 17:45, Stefano Garzarella wrote: >>>>>>>>> On Thu, May 20, 2021 at 10:17:58PM +0300, Arseny Krasnov wrote: >>>>>>>>>> Callback fetches RW packets from rx queue of socket until whole record >>>>>>>>>> is copied(if user's buffer is full, user is not woken up). This is done >>>>>>>>>> to not stall sender, because if we wake up user and it leaves syscall, >>>>>>>>>> nobody will send credit update for rest of record, and sender will wait >>>>>>>>>> for next enter of read syscall at receiver's side. So if user buffer is >>>>>>>>>> full, we just send credit update and drop data. >>>>>>>>>> >>>>>>>>>> Signed-off-by: Arseny Krasnov >>>>>>>>>> --- >>>>>>>>>> v9 -> v10: >>>>>>>>>> 1) Number of dequeued bytes incremented even in case when >>>>>>>>>> user's buffer is full. >>>>>>>>>> 2) Use 'msg_data_left()' instead of direct access to 'msg_hdr'. >>>>>>>>>> 3) Rename variable 'err' to 'dequeued_len', in case of error >>>>>>>>>> it has negative value. >>>>>>>>>> >>>>>>>>>> include/linux/virtio_vsock.h | 5 ++ >>>>>>>>>> net/vmw_vsock/virtio_transport_common.c | 65 +++++++++++++++++++++++++ >>>>>>>>>> 2 files changed, 70 insertions(+) >>>>>>>>>> >>>>>>>>>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h >>>>>>>>>> index dc636b727179..02acf6e9ae04 100644 >>>>>>>>>> --- a/include/linux/virtio_vsock.h >>>>>>>>>> +++ b/include/linux/virtio_vsock.h >>>>>>>>>> @@ -80,6 +80,11 @@ virtio_transport_dgram_dequeue(struct vsock_sock *vsk, >>>>>>>>>> struct msghdr *msg, >>>>>>>>>> size_t len, int flags); >>>>>>>>>> >>>>>>>>>> +ssize_t >>>>>>>>>> +virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk, >>>>>>>>>> + struct msghdr *msg, >>>>>>>>>> + int flags, >>>>>>>>>> + bool *msg_ready); >>>>>>>>>> s64 virtio_transport_stream_has_data(struct vsock_sock *vsk); >>>>>>>>>> s64 virtio_transport_stream_has_space(struct vsock_sock *vsk); >>>>>>>>>> >>>>>>>>>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >>>>>>>>>> index ad0d34d41444..61349b2ea7fe 100644 >>>>>>>>>> --- a/net/vmw_vsock/virtio_transport_common.c >>>>>>>>>> +++ b/net/vmw_vsock/virtio_transport_common.c >>>>>>>>>> @@ -393,6 +393,59 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk, >>>>>>>>>> return err; >>>>>>>>>> } >>>>>>>>>> >>>>>>>>>> +static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk, >>>>>>>>>> + struct msghdr *msg, >>>>>>>>>> + int flags, >>>>>>>>>> + bool *msg_ready) >>>>>>>>>> +{ >>>>>>>>>> + struct virtio_vsock_sock *vvs = vsk->trans; >>>>>>>>>> + struct virtio_vsock_pkt *pkt; >>>>>>>>>> + int dequeued_len = 0; >>>>>>>>>> + size_t user_buf_len = msg_data_left(msg); >>>>>>>>>> + >>>>>>>>>> + *msg_ready = false; >>>>>>>>>> + spin_lock_bh(&vvs->rx_lock); >>>>>>>>>> + >>>>>>>>>> + while (!*msg_ready && !list_empty(&vvs->rx_queue) && dequeued_len >= 0) { >>>>>>>>> I' >>>>>>>>> >>>>>>>>>> + size_t bytes_to_copy; >>>>>>>>>> + size_t pkt_len; >>>>>>>>>> + >>>>>>>>>> + pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list); >>>>>>>>>> + pkt_len = (size_t)le32_to_cpu(pkt->hdr.len); >>>>>>>>>> + bytes_to_copy = min(user_buf_len, pkt_len); >>>>>>>>>> + >>>>>>>>>> + if (bytes_to_copy) { >>>>>>>>>> + /* sk_lock is held by caller so no one else can dequeue. >>>>>>>>>> + * Unlock rx_lock since memcpy_to_msg() may sleep. >>>>>>>>>> + */ >>>>>>>>>> + spin_unlock_bh(&vvs->rx_lock); >>>>>>>>>> + >>>>>>>>>> + if (memcpy_to_msg(msg, pkt->buf, bytes_to_copy)) >>>>>>>>>> + dequeued_len = -EINVAL; >>>>>>>>> I think here is better to return the error returned by memcpy_to_msg(), >>>>>>>>> as we do in the other place where we use memcpy_to_msg(). >>>>>>>>> >>>>>>>>> I mean something like this: >>>>>>>>> err = memcpy_to_msgmsg, pkt->buf, bytes_to_copy); >>>>>>>>> if (err) >>>>>>>>> dequeued_len = err; >>>>>>>> Ack >>>>>>>>>> + else >>>>>>>>>> + user_buf_len -= bytes_to_copy; >>>>>>>>>> + >>>>>>>>>> + spin_lock_bh(&vvs->rx_lock); >>>>>>>>>> + } >>>>>>>>>> + >>>>>>>>> Maybe here we can simply break the cycle if we have an error: >>>>>>>>> if (dequeued_len < 0) >>>>>>>>> break; >>>>>>>>> >>>>>>>>> Or we can refactor a bit, simplifying the while() condition and also the >>>>>>>>> code in this way (not tested): >>>>>>>>> >>>>>>>>> while (!*msg_ready && !list_empty(&vvs->rx_queue)) { >>>>>>>>> ... >>>>>>>>> >>>>>>>>> if (bytes_to_copy) { >>>>>>>>> int err; >>>>>>>>> >>>>>>>>> /* ... >>>>>>>>> */ >>>>>>>>> spin_unlock_bh(&vvs->rx_lock); >>>>>>>>> err = memcpy_to_msgmsg, pkt->buf, bytes_to_copy); >>>>>>>>> if (err) { >>>>>>>>> dequeued_len = err; >>>>>>>>> goto out; >>>>>>>>> } >>>>>>>>> spin_lock_bh(&vvs->rx_lock); >>>>>>>>> >>>>>>>>> user_buf_len -= bytes_to_copy; >>>>>>>>> } >>>>>>>>> >>>>>>>>> dequeued_len += pkt_len; >>>>>>>>> >>>>>>>>> if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) >>>>>>>>> *msg_ready = true; >>>>>>>>> >>>>>>>>> virtio_transport_dec_rx_pkt(vvs, pkt); >>>>>>>>> list_del(&pkt->list); >>>>>>>>> virtio_transport_free_pkt(pkt); >>>>>>>>> } >>>>>>>>> >>>>>>>>> out: >>>>>>>>> spin_unlock_bh(&vvs->rx_lock); >>>>>>>>> >>>>>>>>> virtio_transport_send_credit_update(vsk); >>>>>>>>> >>>>>>>>> return dequeued_len; >>>>>>>>> } >>>>>>>> I think we can't do 'goto out' or break, because in case of error, >>>>>>>> we still need >>>>>>>> to free packet. >>>>>>> Didn't we have code that remove packets from a previous message? >>>>>>> I don't see it anymore. >>>>>>> >>>>>>> For example if we have 10 packets queued for a message (the 10th >>>>>>> packet >>>>>>> has the EOR flag) and the memcpy_to_msg() fails on the 2nd packet, with >>>>>>> you proposal we are freeing only the first 2 packets, the rest is there >>>>>>> and should be freed when reading the next message, but I don't see that >>>>>>> code. >>>>>>> >>>>>>> The same can happen if the recvmsg syscall is interrupted. In that case >>>>>>> we report that nothing was copied, but we freed the first N packets, so >>>>>>> they are lost but the other packets are still in the queue. >>>>>>> >>>>>>> Please check also the patch where we implemented >>>>>>> __vsock_seqpacket_recvmsg(). >>>>>>> >>>>>>> I thinks we should free packets only when we are sure we copied them to >>>>>>> the user space. >>>>>> Hm, yes, this is problem. To solve it i can restore previous approach >>>>>> with seqbegin/seqend. In that case i can detect unfinished record and >>>>>> drop it's packets. Seems seqbegin will be a bit like >>>>>> VIRTIO_VSOCK_SEQ_EOR in flags >>>>>> field of header(e.g. VIRTIO_VSOCK_SEQ_BEGIN). Message id and length are >>>>>> unneeded, >>>>>> as channel considedered lossless. What do You think? >>>>>> >>>>> I think VIRTIO_VSOCK_SEQ_BEGIN is redundant, using only EOR should be >>>>> fine. >>>>> >>>>> When we receive EOR we know that this is the last packet on this message >>>>> and the next packet will be the first of a new message. >>>>> >>>>> What we should do is check that we have all the fragments of a packet >>>>> and return them all together, otherwise we have to say we have nothing. >>>>> >>>>> For example as we process packets from the vitqueue and queue them in >>>>> the rx_queue we could use a counter of how many EORs are in the >>>>> rx_queue, which we decrease in virtio_transport_seqpacket_do_dequeue() >>>>> when we copied all the fragments. >>>>> >>>>> If the counter is 0, we don't remove anything from the queue and >>>>> virtio_transport_seqpacket_do_dequeue() returns 0. >>>>> >>>>> So .seqpacket_dequeue should return 0 if there is not at least one >>>>> complete message, or return the entire message. A partial message should >>>>> never return. >>>>> >>>>> What do you think? >>>> I like it, i've implemented this approach in some early pre v1 versions. >>>> >>>> But in this case, credit update logic will be changed - in current implementation >>>> >>>> (both seqpacket and stream) credit update reply is sent when data is copied >>>> >>>> to user's buffer(e.g. we copy data somewhere, free packet and ready to process >>>> >>>> new packet). But if we don't touch user's buffer and keeping incoming packet in rx queue >>>> >>>> until whole record is ready, when to send credit update? >>> I think the best approach could be to send credit updates when we remove >>> them from the rx_queue. >> In that case, it will be impossible to send message bigger than size of rx buffer >> >> (e.g. credit allowed size), because packet will be queued without credit update >> >> reply until credit allowed reach 0. >> > Yep, but I think it is a reasonable limit for a datagram socket. > > Maybe we can add a check on the TX side, since we know this value and > return an error to the user. E.g., to before sending message  using SEQPACKET socket, i need to call setsockopt with SO_VM_SOCKETS_BUFFER_MAX_SIZE/ SO_VM_SOCKETS_BUFFER_SIZE params to setup maximum message size, if user tries to send message bigger than it, return -EMSGSIZE ? Thank You > > Thanks, > Stefano > >