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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id B317EC48BC4 for ; Tue, 20 Feb 2024 11:44:43 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rcOXE-00025b-Vi; Tue, 20 Feb 2024 06:43:41 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rcOXD-00022w-2f for qemu-devel@nongnu.org; Tue, 20 Feb 2024 06:43:39 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rcOXB-0004sX-7m for qemu-devel@nongnu.org; Tue, 20 Feb 2024 06:43:38 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1708429416; 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=mNLtF8khbNBYYvI2PfRHikj0zkmpfthOY0y5Gq+pOEA=; b=jAq25FY077EehrxBdVnq/GzFQFayDYAUgO/UTLJnc+kbC9wFVHDAMZq6NF8umW84S0VZG8 HfVk2AF1fPWWHUuGC3B7WGuVQsOhqnXfDJBRBZFS6DYRCc0DWby6QkKjqm0/r58Q8O7NLB rKcMvt5tJnH/7E9nh3QWP97XJCj4IVw= Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-12-tpaTnpuINcCgItXnxpOT_g-1; Tue, 20 Feb 2024 06:43:34 -0500 X-MC-Unique: tpaTnpuINcCgItXnxpOT_g-1 Received: by mail-ej1-f72.google.com with SMTP id a640c23a62f3a-a357c92f241so190820166b.0 for ; Tue, 20 Feb 2024 03:43:34 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708429413; x=1709034213; 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=mNLtF8khbNBYYvI2PfRHikj0zkmpfthOY0y5Gq+pOEA=; b=LqESt4qPjNmAr1xBPMjZ54PTZagOFJ6qn7UHHgH+2LyJzyOX2mRtjfYGcdoM0SiKVK G3WvpYXXgXEvurAqPDROTxRAo18YQpj6nr9PxNUxFOrayXgOFP5BG5g4ntXNS8B71aLC 85rQhZ9Po1QSX97x16uYJGd7uZbPD70R8s8KHuDx0O/hTquVjnFLobMmuzmjeQlzNT68 dZOOEPcfFxTwu0FaW76HPO9bNgimfhKgSX+1leaIcuWOb4o0mNjr2RyNCgCARcX3m+aB Wiu0awvK3Dfbh6XgwVFqHIII7KvrBz4cmCEcPUYEhJFMZeIW4JgTA9OQNPXeeYahBt9j Dy8Q== X-Forwarded-Encrypted: i=1; AJvYcCUftiq6aJBhntTepqI3vGcsRMCy6Qv/C8j49dTmP2FvW64GRzFEqr/1k60RNvJitgyyAWIAKLPHIgwaohq6dgnlL8JqhtM= X-Gm-Message-State: AOJu0Yzbepdp/x/Fzwfue/KFaFIltWAp44S5kiCyyAI0MEZJd2Zhh3Br /Ubu5maPk/jRe73M3m9hph4BMKTP+24fql5mojqvIpiNV0lYIkbs6mDRiZOLoGgYCtfXkZTsAMz KylhSvrpWQWxtfwLRrUrdwUxbxfobTCepsbU2aqKVvayoXlwJ58sJ/jaLCi56 X-Received: by 2002:a17:906:ae9b:b0:a3e:e84b:232 with SMTP id md27-20020a170906ae9b00b00a3ee84b0232mr1432278ejb.75.1708429413098; Tue, 20 Feb 2024 03:43:33 -0800 (PST) X-Google-Smtp-Source: AGHT+IFlKsV41ccovpESY8FLmokS1su2g0EFEd0hWd0/2A9hOs7kINal5snMBJtIjnrAoE9dgEyLYw== X-Received: by 2002:a17:906:ae9b:b0:a3e:e84b:232 with SMTP id md27-20020a170906ae9b00b00a3ee84b0232mr1432269ejb.75.1708429412708; Tue, 20 Feb 2024 03:43:32 -0800 (PST) Received: from redhat.com ([2a02:14f:175:1376:5352:3710:49bb:419e]) by smtp.gmail.com with ESMTPSA id u23-20020a170906c41700b00a3d81b90ffcsm3870512ejz.218.2024.02.20.03.43.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Feb 2024 03:43:32 -0800 (PST) Date: Tue, 20 Feb 2024 06:43:28 -0500 From: "Michael S. Tsirkin" To: Maxime Coquelin Cc: Hao Chen , "open list:All patches CC here" , huangml@yusur.tech, zy@yusur.tech Subject: Re: [PATCH] vhost-user: fix the issue of vhost deadlock in nested virtualization Message-ID: <20240220064027-mutt-send-email-mst@kernel.org> References: <20240126100737.2509847-1-chenh@yusur.tech> <20240213050258-mutt-send-email-mst@kernel.org> <5176a8e4-dbdc-45e0-a1f2-d9cb3b71a6b1@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5176a8e4-dbdc-45e0-a1f2-d9cb3b71a6b1@redhat.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.05, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Feb 20, 2024 at 12:26:49PM +0100, Maxime Coquelin wrote: > > > On 2/13/24 11:05, Michael S. Tsirkin wrote: > > On Fri, Jan 26, 2024 at 06:07:37PM +0800, Hao Chen wrote: > > > I run "dpdk-vdpa" and "qemur-L2" in "qemu-L1". > > > > > > In a nested virtualization environment, "qemu-L2" vhost-user socket sends > > > a "VHOST_USER_IOTLB_MSG" message to "dpdk-vdpa" and blocks waiting for > > > "dpdk-vdpa" to process the message. > > > If "dpdk-vdpa" doesn't complete the processing of the "VHOST_USER_IOTLB_MSG" > > > message and sends a message that needs to be replied in another thread, > > > such as "VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG", "dpdk-vdpa" will also > > > block and wait for "qemu-L2" to process this message. However, "qemu-L2" > > > vhost-user's socket is blocking while waiting for a reply from "dpdk-vdpa" > > > after processing the message "VHOSTr_USER_IOTLB_MSG", and > > > "VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG" will not be processed. > > > In this case, both "dpdk-vdpa" and "qemu-L2" are blocked on the > > > vhost read, resulting in a deadlock. > > > > > > You can modify "VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG" or > > > "VHOST_USER_IOTLB_MSG" to "no need reply" to fix this issue. > > > There are too many messages in dpdk that are similar to > > > "VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG", and I would prefer the latter. > > > > > > Fixes: 24e34754eb78 ("vhost-user: factor out msg head and payload") > > > > > > Signed-off-by: Hao Chen > > > > I would be very worried that IOTLB becomes stale and > > guest memory is corrupted if we just proceed without waiting. > > > > Maxime what do you think? How would you address the issue? > > I agree with you, this is not possible. > For example, in case of IOTLB invalidate, the frontend relies on the > backend reply to ensure it is no more accessing the memory before > proceeding. > > The reply-ack for VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG request is > less important, if it fails the host notifications won't work but would > not risk corruption. Maybe on Qemu side we could fail init if processing > the request fails, as I think that if negotiated, we can expect it to > succeed. > > What do you think about this proposal? > > Regards, > Maxime Fundamentally, I think that if qemu blocks guest waiting for a rely that is ok but it really has to process incoming messages meanwhile. Same should apply to backend I think ... > > > > > > > --- > > > hw/virtio/vhost-user.c | 10 ++-------- > > > 1 file changed, 2 insertions(+), 8 deletions(-) > > > > > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > > > index f214df804b..02caa94b6c 100644 > > > --- a/hw/virtio/vhost-user.c > > > +++ b/hw/virtio/vhost-user.c > > > @@ -2371,20 +2371,14 @@ static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu) > > > static int vhost_user_send_device_iotlb_msg(struct vhost_dev *dev, > > > struct vhost_iotlb_msg *imsg) > > > { > > > - int ret; > > > VhostUserMsg msg = { > > > .hdr.request = VHOST_USER_IOTLB_MSG, > > > .hdr.size = sizeof(msg.payload.iotlb), > > > - .hdr.flags = VHOST_USER_VERSION | VHOST_USER_NEED_REPLY_MASK, > > > + .hdr.flags = VHOST_USER_VERSION, > > > .payload.iotlb = *imsg, > > > }; > > > - ret = vhost_user_write(dev, &msg, NULL, 0); > > > - if (ret < 0) { > > > - return ret; > > > - } > > > - > > > - return process_message_reply(dev, &msg); > > > + return vhost_user_write(dev, &msg, NULL, 0); > > > } > > > -- > > > 2.27.0 > >