From patchwork Fri Aug 19 05:21:58 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arseniy Krasnov X-Patchwork-Id: 12948324 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30632C28B2B for ; Fri, 19 Aug 2022 05:22:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238595AbiHSFWb (ORCPT ); Fri, 19 Aug 2022 01:22:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241654AbiHSFWa (ORCPT ); Fri, 19 Aug 2022 01:22:30 -0400 Received: from mail.sberdevices.ru (mail.sberdevices.ru [45.89.227.171]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B48A5E01C2; Thu, 18 Aug 2022 22:22:27 -0700 (PDT) Received: from s-lin-edge02.sberdevices.ru (localhost [127.0.0.1]) by mail.sberdevices.ru (Postfix) with ESMTP id 0860D5FD07; Fri, 19 Aug 2022 08:22:26 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sberdevices.ru; s=mail; t=1660886546; bh=GooZAVHnzepBYKSNfdd8aQsvtHUU6TX2S4d+v+I+b5A=; h=From:To:Subject:Date:Message-ID:Content-Type:MIME-Version; b=gWXX37n6OWek1Tn13sSWrePrmJlZWkOMfAwk1K9RHcopEiyS5ph67ICXSOjz+whrB d8ItdpjOFRvIphMxg1rlNxIifJEFH3BywI9FcuqpqKDR0dB8BVIPJk7T8H6i8TxOCO gpwQ6DeFaSDoC3zR/UEozuHx2sZc7Uah8bdKd6QElN4oTO7YAy9j4XZFGVi2QyTr7z rTVojXRzVW3U4zeMFs1L9HfGI/VeTWskm+/2zAhAdDZGrUxMzKNr0C6/dmDC6aZ5g0 DJkTu2ghabQx2IZiddvWHWQlG82MjWlIwa+jbjXt4Qk+FsGgPYEGW/h2HG7WejpI19 jirpVG+AZS2/g== Received: from S-MS-EXCH02.sberdevices.ru (S-MS-EXCH02.sberdevices.ru [172.16.1.5]) by mail.sberdevices.ru (Postfix) with ESMTP; Fri, 19 Aug 2022 08:22:24 +0300 (MSK) From: Arseniy Krasnov To: Stefano Garzarella , "David S. Miller" , "edumazet@google.com" , "Jakub Kicinski" , Paolo Abeni , "kys@microsoft.com" , "haiyangz@microsoft.com" , "sthemmin@microsoft.com" , "wei.liu@kernel.org" , Dexuan Cui , Stefan Hajnoczi , Bryan Tan , Vishnu Dasa , Krasnov Arseniy , "Michael S. Tsirkin" CC: "virtualization@lists.linux-foundation.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-hyperv@vger.kernel.org" , "kvm@vger.kernel.org" , kernel , VMware PV-Drivers Reviewers Subject: [PATCH net-next v4 0/9] vsock: updates for SO_RCVLOWAT handling Thread-Topic: [PATCH net-next v4 0/9] vsock: updates for SO_RCVLOWAT handling Thread-Index: AQHYs4uayjgwUp42sUeXUj6ZEfA4aQ== Date: Fri, 19 Aug 2022 05:21:58 +0000 Message-ID: Accept-Language: en-US, ru-RU Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [172.16.1.12] Content-ID: MIME-Version: 1.0 X-KSMG-Rule-ID: 4 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 1.1.2.30, bases: 2022/08/19 00:26:00 #20118704 X-KSMG-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hello, This patchset includes some updates for SO_RCVLOWAT: 1) af_vsock: During my experiments with zerocopy receive, i found, that in some cases, poll() implementation violates POSIX: when socket has non- default SO_RCVLOWAT(e.g. not 1), poll() will always set POLLIN and POLLRDNORM bits in 'revents' even number of bytes available to read on socket is smaller than SO_RCVLOWAT value. In this case,user sees POLLIN flag and then tries to read data(for example using 'read()' call), but read call will be blocked, because SO_RCVLOWAT logic is supported in dequeue loop in af_vsock.c. But the same time, POSIX requires that: "POLLIN Data other than high-priority data may be read without blocking. POLLRDNORM Normal data may be read without blocking." See https://www.open-std.org/jtc1/sc22/open/n4217.pdf, page 293. So, we have, that poll() syscall returns POLLIN, but read call will be blocked. Also in man page socket(7) i found that: "Since Linux 2.6.28, select(2), poll(2), and epoll(7) indicate a socket as readable only if at least SO_RCVLOWAT bytes are available." I checked TCP callback for poll()(net/ipv4/tcp.c, tcp_poll()), it uses SO_RCVLOWAT value to set POLLIN bit, also i've tested TCP with this case for TCP socket, it works as POSIX required. I've added some fixes to af_vsock.c and virtio_transport_common.c, test is also implemented. 2) virtio/vsock: It adds some optimization to wake ups, when new data arrived. Now, SO_RCVLOWAT is considered before wake up sleepers who wait new data. There is no sense, to kick waiter, when number of available bytes in socket's queue < SO_RCVLOWAT, because if we wake up reader in this case, it will wait for SO_RCVLOWAT data anyway during dequeue, or in poll() case, POLLIN/POLLRDNORM bits won't be set, so such exit from poll() will be "spurious". This logic is also used in TCP sockets. 3) vmci/vsock: Same as 2), but i'm not sure about this changes. Will be very good, to get comments from someone who knows this code. 4) Hyper-V: As Dexuan Cui mentioned, for Hyper-V transport it is difficult to support SO_RCVLOWAT, so he suggested to disable this feature for Hyper-V. Thank You Arseniy Krasnov(9): vsock: SO_RCVLOWAT transport set callback hv_sock: disable SO_RCVLOWAT support virtio/vsock: use 'target' in notify_poll_in callback vmci/vsock: use 'target' in notify_poll_in callback vsock: pass sock_rcvlowat to notify_poll_in as target vsock: add API call for data ready virtio/vsock: check SO_RCVLOWAT before wake up reader vmci/vsock: check SO_RCVLOWAT before wake up reader vsock_test: POLLIN + SO_RCVLOWAT test include/net/af_vsock.h | 2 + net/vmw_vsock/af_vsock.c | 33 +++++++- net/vmw_vsock/hyperv_transport.c | 7 ++ net/vmw_vsock/virtio_transport_common.c | 7 +- net/vmw_vsock/vmci_transport_notify.c | 10 +-- net/vmw_vsock/vmci_transport_notify_qstate.c | 12 +-- tools/testing/vsock/vsock_test.c | 108 +++++++++++++++++++++++++++ 7 files changed, 162 insertions(+), 17 deletions(-) Changelog: v1 -> v2: 1) Patches for VMCI transport(same as for virtio-vsock). 2) Patches for Hyper-V transport(disabling SO_RCVLOWAT setting). 3) Waiting logic in test was updated(sleep() -> poll()). v2 -> v3: 1) Patches were reordered. 2) Commit message updated in 0005. 3) Check 'transport' pointer in 0001 for NULL. v3 -> v4: 1) vsock_set_rcvlowat() logic changed. Previous version required assigned transport and always called its 'set_rcvlowat' callback (if present). Now, assignment is not needed. 2) 0003,0004,0005,0006,0007,0008 - commit messages updated. 3) 0009 - small refactoring and style fixes. 4) RFC tag was removed.