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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 CE56FC433E0 for ; Tue, 19 May 2020 09:14:29 +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 8F7DA20756 for ; Tue, 19 May 2020 09:14:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="tuPLQW7y" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F7DA20756 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=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:34896 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jayKS-0004RL-RE for qemu-devel@archiver.kernel.org; Tue, 19 May 2020 05:14:28 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57692) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jayJe-0003dm-0H; Tue, 19 May 2020 05:13:38 -0400 Received: from forwardcorp1o.mail.yandex.net ([95.108.205.193]:50018) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jayJb-00026r-VX; Tue, 19 May 2020 05:13:37 -0400 Received: from mxbackcorp1o.mail.yandex.net (mxbackcorp1o.mail.yandex.net [IPv6:2a02:6b8:0:1a2d::301]) by forwardcorp1o.mail.yandex.net (Yandex) with ESMTP id 61A2F2E08AD; Tue, 19 May 2020 12:13:32 +0300 (MSK) Received: from sas1-9998cec34266.qloud-c.yandex.net (sas1-9998cec34266.qloud-c.yandex.net [2a02:6b8:c14:3a0e:0:640:9998:cec3]) by mxbackcorp1o.mail.yandex.net (mxbackcorp/Yandex) with ESMTP id RQTKa9yvxl-DSYGBxk8; Tue, 19 May 2020 12:13:32 +0300 Precedence: bulk DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1589879612; bh=UR17DxhJGsImtCX1AbVfD4kZ0NucogGtVot4AW6j6b0=; h=In-Reply-To:Message-ID:Subject:To:From:References:Date:Cc; b=tuPLQW7yIpS02VU6GxfsZ5KIWBTFQmX+UtAbubsiJLjNzFa1KY3xqKjywTwM1AA7O 1GSClzZXsf2DXbNv5fkNbzV6n/Owg8pnA5+fBloP/2T7ozjqceEnVCJipcqFDJ7EQA FcgK108/aHHiBHfGvD5Wnt8gOMxsYcXLYtYmhSlk= Authentication-Results: mxbackcorp1o.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-vpn.dhcp.yndx.net (dynamic-vpn.dhcp.yndx.net [2a02:6b8:b081:302::1:a]) by sas1-9998cec34266.qloud-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id 9LdbBAURLA-DSWWQMqF; Tue, 19 May 2020 12:13:28 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Date: Tue, 19 May 2020 12:13:27 +0300 From: Dima Stepanov To: Jason Wang Subject: Re: [PATCH v2 5/5] vhost: add device started check in migration set log Message-ID: <20200519091319.GA17982@dimastep-nix> References: <20200511092541.GA27558@dimastep-nix> <20200512093521.GA5363@dimastep-nix> <20200512235934-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Received-SPF: pass client-ip=95.108.205.193; envelope-from=dimastep@yandex-team.ru; helo=forwardcorp1o.mail.yandex.net X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/19 05:13:32 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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: fam@euphon.net, kwolf@redhat.com, stefanha@redhat.com, qemu-block@nongnu.org, "Michael S. Tsirkin" , qemu-devel@nongnu.org, dgilbert@redhat.com, arei.gonglei@huawei.com, fengli@smartx.com, yc-core@yandex-team.ru, pbonzini@redhat.com, marcandre.lureau@redhat.com, raphael.norwitz@nutanix.com, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, May 13, 2020 at 01:56:18PM +0800, Jason Wang wrote: > > On 2020/5/13 下午12:15, Michael S. Tsirkin wrote: > >On Tue, May 12, 2020 at 12:35:30PM +0300, Dima Stepanov wrote: > >>On Tue, May 12, 2020 at 11:32:50AM +0800, Jason Wang wrote: > >>>On 2020/5/11 下午5:25, Dima Stepanov wrote: > >>>>On Mon, May 11, 2020 at 11:15:53AM +0800, Jason Wang wrote: > >>>>>On 2020/4/30 下午9:36, Dima Stepanov wrote: > >>>>>>If vhost-user daemon is used as a backend for the vhost device, then we > >>>>>>should consider a possibility of disconnect at any moment. If such > >>>>>>disconnect happened in the vhost_migration_log() routine the vhost > >>>>>>device structure will be clean up. > >>>>>>At the start of the vhost_migration_log() function there is a check: > >>>>>> if (!dev->started) { > >>>>>> dev->log_enabled = enable; > >>>>>> return 0; > >>>>>> } > >>>>>>To be consistent with this check add the same check after calling the > >>>>>>vhost_dev_set_log() routine. This in general help not to break a > >>>>>>migration due the assert() message. But it looks like that this code > >>>>>>should be revised to handle these errors more carefully. > >>>>>> > >>>>>>In case of vhost-user device backend the fail paths should consider the > >>>>>>state of the device. In this case we should skip some function calls > >>>>>>during rollback on the error paths, so not to get the NULL dereference > >>>>>>errors. > >>>>>> > >>>>>>Signed-off-by: Dima Stepanov > >>>>>>--- > >>>>>> hw/virtio/vhost.c | 39 +++++++++++++++++++++++++++++++++++---- > >>>>>> 1 file changed, 35 insertions(+), 4 deletions(-) > >>>>>> > >>>>>>diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > >>>>>>index 3ee50c4..d5ab96d 100644 > >>>>>>--- a/hw/virtio/vhost.c > >>>>>>+++ b/hw/virtio/vhost.c > >>>>>>@@ -787,6 +787,17 @@ static int vhost_dev_set_features(struct vhost_dev *dev, > >>>>>> static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log) > >>>>>> { > >>>>>> int r, i, idx; > >>>>>>+ > >>>>>>+ if (!dev->started) { > >>>>>>+ /* > >>>>>>+ * If vhost-user daemon is used as a backend for the > >>>>>>+ * device and the connection is broken, then the vhost_dev > >>>>>>+ * structure will be reset all its values to 0. > >>>>>>+ * Add additional check for the device state. > >>>>>>+ */ > >>>>>>+ return -1; > >>>>>>+ } > >>>>>>+ > >>>>>> r = vhost_dev_set_features(dev, enable_log); > >>>>>> if (r < 0) { > >>>>>> goto err_features; > >>>>>>@@ -801,12 +812,19 @@ static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log) > >>>>>> } > >>>>>> return 0; > >>>>>> err_vq: > >>>>>>- for (; i >= 0; --i) { > >>>>>>+ /* > >>>>>>+ * Disconnect with the vhost-user daemon can lead to the > >>>>>>+ * vhost_dev_cleanup() call which will clean up vhost_dev > >>>>>>+ * structure. > >>>>>>+ */ > >>>>>>+ for (; dev->started && (i >= 0); --i) { > >>>>>> idx = dev->vhost_ops->vhost_get_vq_index( > >>>>>Why need the check of dev->started here, can started be modified outside > >>>>>mainloop? If yes, I don't get the check of !dev->started in the beginning of > >>>>>this function. > >>>>> > >>>>No dev->started can't change outside the mainloop. The main problem is > >>>>only for the vhost_user_blk daemon. Consider the case when we > >>>>successfully pass the dev->started check at the beginning of the > >>>>function, but after it we hit the disconnect on the next call on the > >>>>second or third iteration: > >>>> r = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx, enable_log); > >>>>The unix socket backend device will call the disconnect routine for this > >>>>device and reset the structure. So the structure will be reset (and > >>>>dev->started set to false) inside this set_addr() call. > >>>I still don't get here. I think the disconnect can not happen in the middle > >>>of vhost_dev_set_log() since both of them were running in mainloop. And even > >>>if it can, we probably need other synchronization mechanism other than > >>>simple check here. > >>Disconnect isn't happened in the separate thread it is happened in this > >>routine inside vhost_dev_set_log. When for instance vhost_user_write() > >>call failed: > >> vhost_user_set_log_base() > >> vhost_user_write() > >> vhost_user_blk_disconnect() > >> vhost_dev_cleanup() > >> vhost_user_backend_cleanup() > >>So the point is that if we somehow got a disconnect with the > >>vhost-user-blk daemon before the vhost_user_write() call then it will > >>continue clean up by running vhost_user_blk_disconnect() function. I > >>wrote a more detailed backtrace stack in the separate thread, which is > >>pretty similar to what we have here: > >> Re: [PATCH v2 4/5] vhost: check vring address before calling unmap > >>The places are different but the problem is pretty similar. > >> > >>So if vhost-user commands handshake then everything is fine and > >>reconnect will work as expected. The only problem is how to handle > >>reconnect properly between vhost-user command send/receive. > > > >So vhost net had this problem too. > > > >commit e7c83a885f865128ae3cf1946f8cb538b63cbfba > >Author: Marc-André Lureau > >Date: Mon Feb 27 14:49:56 2017 +0400 > > > > vhost-user: delay vhost_user_stop > > Since commit b0a335e351103bf92f3f9d0bd5759311be8156ac, a socket write > > may trigger a disconnect events, calling vhost_user_stop() and clearing > > all the vhost_dev strutures holding data that vhost.c functions expect > > to remain valid. Delay the cleanup to keep the vhost_dev structure > > valid during the vhost.c functions. > > Signed-off-by: Marc-André Lureau > > Message-id:20170227104956.24729-1-marcandre.lureau@redhat.com > > Signed-off-by: Peter Maydell > > > >it now has this code to address this: > > > > > > case CHR_EVENT_CLOSED: > > /* a close event may happen during a read/write, but vhost > > * code assumes the vhost_dev remains setup, so delay the > > * stop & clear to idle. > > * FIXME: better handle failure in vhost code, remove bh > > */ > > if (s->watch) { > > AioContext *ctx = qemu_get_current_aio_context(); > > > > g_source_remove(s->watch); > > s->watch = 0; > > qemu_chr_fe_set_handlers(&s->chr, NULL, NULL, NULL, NULL, > > NULL, NULL, false); > > > > aio_bh_schedule_oneshot(ctx, chr_closed_bh, opaque); > > } > > break; > > > >I think it's time we dropped the FIXME and moved the handling to common > >code. Jason? Marc-André? > > > I agree. Just to confirm, do you prefer bh or doing changes like what is > done in this series? It looks to me bh can have more easier codes. While we still having the discussion about migration and its states, i think we can split this patchset. The first patchset will be about fixing the vhost-usr-blk reconnect issues. And the follow up patchset will be about migration if we decide to fix/workaround this abort() call at the start of migration. I'll prepare v3 with this bh approach and will send it for review. What do you think? Thanks, Dima. > > Thanks > > > > > > > > > > > > >