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=-17.3 required=3.0 tests=BAYES_00,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=ham 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 99747C4338F for ; Mon, 9 Aug 2021 09:09:14 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 944AB61075 for ; Mon, 9 Aug 2021 09:09:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 944AB61075 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=yandex-team.ru Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:49792 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mD1HU-0006ND-N6 for qemu-devel@archiver.kernel.org; Mon, 09 Aug 2021 05:09:12 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35896) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mD1Da-0003GF-Q3 for qemu-devel@nongnu.org; Mon, 09 Aug 2021 05:05:12 -0400 Received: from forwardcorp1p.mail.yandex.net ([77.88.29.217]:49932) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mD1DY-0004HG-F3 for qemu-devel@nongnu.org; Mon, 09 Aug 2021 05:05:10 -0400 Received: from iva8-c5ee4261001e.qloud-c.yandex.net (iva8-c5ee4261001e.qloud-c.yandex.net [IPv6:2a02:6b8:c0c:a8a6:0:640:c5ee:4261]) by forwardcorp1p.mail.yandex.net (Yandex) with ESMTP id 7EF842E16D1; Mon, 9 Aug 2021 12:05:06 +0300 (MSK) Received: from iva8-5ba4ca89b0c6.qloud-c.yandex.net (iva8-5ba4ca89b0c6.qloud-c.yandex.net [2a02:6b8:c0c:a8ae:0:640:5ba4:ca89]) by iva8-c5ee4261001e.qloud-c.yandex.net (mxbackcorp/Yandex) with ESMTP id v9V2R81Ga9-56xa8cg9; Mon, 09 Aug 2021 12:05:06 +0300 Precedence: bulk DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1628499906; bh=as0y/lRAF4BAxuKcHrHEEkhHOGFxQ9V3UIAKmJvY0Ng=; h=In-Reply-To:References:Date:Message-ID:From:To:Subject:Cc; b=RKCc6+Mg2RBU/JZOxK0fpkO1wwQaCUObpAC+nbsOUpza2uU0JO46vhZppQLzVWwC0 S/EI5hCZNvU1KLJZkB+MxrgFEp8klvMXMH4kXy8g8ZbtOzUi6g5MDU2pHC60x7fPbv Pp0u3oetZacTu22kPCrg2CWKyd0JYgndzH04hGtw= Authentication-Results: iva8-c5ee4261001e.qloud-c.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-vpn.dhcp.yndx.net (dynamic-vpn.dhcp.yndx.net [2a02:6b8:b081:8001::1:27]) by iva8-5ba4ca89b0c6.qloud-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id 08HepuUqsr-562uqNOv; Mon, 09 Aug 2021 12:05:06 +0300 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client certificate not present) Subject: Re: [PATCH v2] vhost: make SET_VRING_ADDR, SET_FEATURES send replies To: "Michael S. Tsirkin" References: <20210719142138.24543-1-den-plotnikov@yandex-team.ru> <20210803105909-mutt-send-email-mst@kernel.org> From: Denis Plotnikov Message-ID: <386f5100-6527-35e5-db9b-3f4e78c10c25@yandex-team.ru> Date: Mon, 9 Aug 2021 12:05:05 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210803105909-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Received-SPF: pass client-ip=77.88.29.217; envelope-from=den-plotnikov@yandex-team.ru; helo=forwardcorp1p.mail.yandex.net X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, yc-core@yandex-team.ru Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 03.08.2021 18:05, Michael S. Tsirkin wrote: > On Mon, Jul 19, 2021 at 05:21:38PM +0300, Denis Plotnikov wrote: >> On vhost-user-blk migration, qemu normally sends a number of commands >> to enable logging if VHOST_USER_PROTOCOL_F_LOG_SHMFD is negotiated. >> Qemu sends VHOST_USER_SET_FEATURES to enable buffers logging and >> VHOST_USER_SET_VRING_ADDR per each started ring to enable "used ring" >> data logging. >> The issue is that qemu doesn't wait for reply from the vhost daemon >> for these commands which may result in races between qemu expectation >> of logging starting and actual login starting in vhost daemon. >> >> The race can appear as follows: on migration setup, qemu enables dirty page >> logging by sending VHOST_USER_SET_FEATURES. The command doesn't arrive to a >> vhost-user-blk daemon immediately and the daemon needs some time to turn the >> logging on internally. If qemu doesn't wait for reply, after sending the >> command, qemu may start migrate memory pages to a destination. At this time, >> the logging may not be actually turned on in the daemon but some guest pages, >> which the daemon is about to write to, may have already been transferred >> without logging to the destination. Since the logging wasn't turned on, >> those pages won't be transferred again as dirty. So we may end up with >> corrupted data on the destination. >> The same scenario is applicable for "used ring" data logging, which is >> turned on with VHOST_USER_SET_VRING_ADDR command. >> >> To resolve this issue, this patch makes qemu wait for the commands result >> explicilty if VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated and >> logging is enabled. >> >> Signed-off-by: Denis Plotnikov >> --- >> v1 -> v2: >> * send reply only when logging is enabled [mst] >> >> v0 -> v1: >> * send reply for SET_VRING_ADDR, SET_FEATURES only [mst] >> >> hw/virtio/vhost-user.c | 37 ++++++++++++++++++++++++++++++++++--- >> 1 file changed, 34 insertions(+), 3 deletions(-) >> >> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c >> index ee57abe04526..133588b3961e 100644 >> --- a/hw/virtio/vhost-user.c >> +++ b/hw/virtio/vhost-user.c >> @@ -1095,6 +1095,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, >> return 0; >> } >> >> +static bool log_enabled(uint64_t features) >> +{ >> + return !!(features & (0x1ULL << VHOST_F_LOG_ALL)); >> +} >> + >> static int vhost_user_set_vring_addr(struct vhost_dev *dev, >> struct vhost_vring_addr *addr) >> { >> @@ -1105,10 +1110,21 @@ static int vhost_user_set_vring_addr(struct vhost_dev *dev, >> .hdr.size = sizeof(msg.payload.addr), >> }; >> >> + bool reply_supported = virtio_has_feature(dev->protocol_features, >> + VHOST_USER_PROTOCOL_F_REPLY_ACK); >> + >> + if (reply_supported && log_enabled(msg.hdr.flags)) { >> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; >> + } >> + >> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { >> return -1; >> } >> >> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { >> + return process_message_reply(dev, &msg); >> + } >> + >> return 0; >> } >> > OK this is good, but the problem is that we then still have a race > if VHOST_USER_PROTOCOL_F_REPLY_ACK is not set. Bummer. > > Let's send VHOST_USER_GET_FEATURES in this case to flush out outstanding > messages? Ok, I've already sent v3 with related changes. > >> @@ -1288,7 +1304,8 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev, >> return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file); >> } >> >> -static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) >> +static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64, >> + bool need_reply) >> { >> VhostUserMsg msg = { >> .hdr.request = request, >> @@ -1297,23 +1314,37 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) >> .hdr.size = sizeof(msg.payload.u64), >> }; >> >> + if (need_reply) { >> + bool reply_supported = virtio_has_feature(dev->protocol_features, >> + VHOST_USER_PROTOCOL_F_REPLY_ACK); >> + if (reply_supported) { >> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; >> + } >> + } >> + >> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { >> return -1; >> } >> >> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { >> + return process_message_reply(dev, &msg); >> + } >> + >> return 0; >> } >> >> static int vhost_user_set_features(struct vhost_dev *dev, >> uint64_t features) >> { >> - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features); >> + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, >> + log_enabled(features)); >> } >> >> static int vhost_user_set_protocol_features(struct vhost_dev *dev, >> uint64_t features) >> { >> - return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features); >> + return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features, >> + false); >> } >> >> static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64) >> -- >> 2.25.1