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=-7.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 D30D6C47089 for ; Fri, 28 May 2021 01:33:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A4DCB613BF for ; Fri, 28 May 2021 01:33:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235876AbhE1Bf3 (ORCPT ); Thu, 27 May 2021 21:35:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:37473 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235598AbhE1Bf2 (ORCPT ); Thu, 27 May 2021 21:35:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622165634; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8EflzxBdWy0wiqxEhDGP+Q2T2EKetKqpgEpZkAeYf/A=; b=S4yJIAdo04HShBOeEztagfuSKahh7K8Fs6P3wYnWR3yYdOQycT+MVrrAoZUfJ93bznh5cW JnMj6D9FZ/Zfkkw+6343e4kc/73qiP1AixXluONg6+MbYoGrOMQN2dxECYmzxslQ0tnPKU CoSeACifCz8qPc/Y4ykVSaIX221zrpc= Received: from mail-pj1-f71.google.com (mail-pj1-f71.google.com [209.85.216.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-269-rMukT_TYPTqpVW76fmsvqA-1; Thu, 27 May 2021 21:33:53 -0400 X-MC-Unique: rMukT_TYPTqpVW76fmsvqA-1 Received: by mail-pj1-f71.google.com with SMTP id v10-20020a17090a7c0ab029015f673a4c30so1612521pjf.5 for ; Thu, 27 May 2021 18:33:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=8EflzxBdWy0wiqxEhDGP+Q2T2EKetKqpgEpZkAeYf/A=; b=eJIxYhWhOIjAbdX8Lb5DGnpuI+1//LP0igVF6qrnm5OABDJ1BfIdKA8kq00HdymBna y/kDCP7rfVMzxoBRO2eGinuHU0iCAPrEy0qebpMBbMgNAipfyVSQvmTWI/fe/pjJUKLO 5kbtrwSGL6LOneMayLdfy0q7l185ZEgGkFpNLP85L4ew8DdZ2fJQzFum3jIBBP/OYqfM qJVPh0RYwGxChJ4JhRvu/XqN0Fkgdl5fAWt8r823acoRm/bUKP66o4eXXGxLCi88/HkZ l4pMyb9cucTTPbXgWl0h2DFIPqc/m+qFJirxdZuO88zt++OtfzPMpO/x5YImQvrBj0dF Z6Aw== X-Gm-Message-State: AOAM532bJEwM0ANT98haV2HecBbDZ5I6NDlddonTGEVXKbAlQa1iehsE 2MvQV6QORh63l7bq4Pw6f9ikqzg9iPlQl51N+qQoxwzBx5EYhJ+D55jCp3tJVbwirNgDAOaMukZ 5Kbc2F8YlHILhQ/+3ABd2iAz5iw== X-Received: by 2002:a17:90a:4d01:: with SMTP id c1mr1544229pjg.113.1622165631945; Thu, 27 May 2021 18:33:51 -0700 (PDT) X-Google-Smtp-Source: ABdhPJydC/stmtwVBAw7vn0dDxdtXv7rokRxoXkgRqgTNFUSMcTPVSj5vrj1iqRSI/twfonCL/POEw== X-Received: by 2002:a17:90a:4d01:: with SMTP id c1mr1544208pjg.113.1622165631682; Thu, 27 May 2021 18:33:51 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id g4sm2964265pgu.46.2021.05.27.18.33.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 May 2021 18:33:51 -0700 (PDT) Subject: Re: [PATCH v7 11/12] vduse: Introduce VDUSE - vDPA Device in Userspace To: Yongji Xie Cc: "Michael S. Tsirkin" , Stefan Hajnoczi , Stefano Garzarella , Parav Pandit , Christoph Hellwig , Christian Brauner , Randy Dunlap , Matthew Wilcox , Al Viro , Jens Axboe , bcrl@kvack.org, Jonathan Corbet , =?UTF-8?Q?Mika_Penttil=c3=a4?= , Dan Carpenter , joro@8bytes.org, virtualization , netdev@vger.kernel.org, kvm , linux-fsdevel@vger.kernel.org, iommu@lists.linux-foundation.org, linux-kernel References: <20210517095513.850-1-xieyongji@bytedance.com> <20210517095513.850-12-xieyongji@bytedance.com> <3740c7eb-e457-07f3-5048-917c8606275d@redhat.com> <5a68bb7c-fd05-ce02-cd61-8a601055c604@redhat.com> <00ded99f-91b6-ba92-5d92-2366b163f129@redhat.com> <3cc7407d-9637-227e-9afa-402b6894d8ac@redhat.com> From: Jason Wang Message-ID: Date: Fri, 28 May 2021 09:33:43 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 在 2021/5/27 下午6:14, Yongji Xie 写道: > On Thu, May 27, 2021 at 4:43 PM Jason Wang wrote: >> >> 在 2021/5/27 下午4:41, Jason Wang 写道: >>> 在 2021/5/27 下午3:34, Yongji Xie 写道: >>>> On Thu, May 27, 2021 at 1:40 PM Jason Wang wrote: >>>>> 在 2021/5/27 下午1:08, Yongji Xie 写道: >>>>>> On Thu, May 27, 2021 at 1:00 PM Jason Wang >>>>>> wrote: >>>>>>> 在 2021/5/27 下午12:57, Yongji Xie 写道: >>>>>>>> On Thu, May 27, 2021 at 12:13 PM Jason Wang >>>>>>>> wrote: >>>>>>>>> 在 2021/5/17 下午5:55, Xie Yongji 写道: >>>>>>>>>> + >>>>>>>>>> +static int vduse_dev_msg_sync(struct vduse_dev *dev, >>>>>>>>>> + struct vduse_dev_msg *msg) >>>>>>>>>> +{ >>>>>>>>>> + init_waitqueue_head(&msg->waitq); >>>>>>>>>> + spin_lock(&dev->msg_lock); >>>>>>>>>> + vduse_enqueue_msg(&dev->send_list, msg); >>>>>>>>>> + wake_up(&dev->waitq); >>>>>>>>>> + spin_unlock(&dev->msg_lock); >>>>>>>>>> + wait_event_killable(msg->waitq, msg->completed); >>>>>>>>> What happens if the userspace(malicous) doesn't give a response >>>>>>>>> forever? >>>>>>>>> >>>>>>>>> It looks like a DOS. If yes, we need to consider a way to fix that. >>>>>>>>> >>>>>>>> How about using wait_event_killable_timeout() instead? >>>>>>> Probably, and then we need choose a suitable timeout and more >>>>>>> important, >>>>>>> need to report the failure to virtio. >>>>>>> >>>>>> Makes sense to me. But it looks like some >>>>>> vdpa_config_ops/virtio_config_ops such as set_status() didn't have a >>>>>> return value. Now I add a WARN_ON() for the failure. Do you mean we >>>>>> need to add some change for virtio core to handle the failure? >>>>> Maybe, but I'm not sure how hard we can do that. >>>>> >>>> We need to change all virtio device drivers in this way. >>> >>> Probably. >>> >>> >>>>> We had NEEDS_RESET but it looks we don't implement it. >>>>> >>>> Could it handle the failure of get_feature() and get/set_config()? >>> >>> Looks not: >>> >>> " >>> >>> The device SHOULD set DEVICE_NEEDS_RESET when it enters an error state >>> that a reset is needed. If DRIVER_OK is set, after it sets >>> DEVICE_NEEDS_RESET, the device MUST send a device configuration change >>> notification to the driver. >>> >>> " >>> >>> This looks implies that NEEDS_RESET may only work after device is >>> probed. But in the current design, even the reset() is not reliable. >>> >>> >>>>> Or a rough idea is that maybe need some relaxing to be coupled loosely >>>>> with userspace. E.g the device (control path) is implemented in the >>>>> kernel but the datapath is implemented in the userspace like TUN/TAP. >>>>> >>>> I think it can work for most cases. One problem is that the set_config >>>> might change the behavior of the data path at runtime, e.g. >>>> virtnet_set_mac_address() in the virtio-net driver and >>>> cache_type_store() in the virtio-blk driver. Not sure if this path is >>>> able to return before the datapath is aware of this change. >>> >>> Good point. >>> >>> But set_config() should be rare: >>> >>> E.g in the case of virtio-net with VERSION_1, config space is read >>> only, and it was set via control vq. >>> >>> For block, we can >>> >>> 1) start from without WCE or >>> 2) we add a config change notification to userspace or >>> 3) extend the spec to use vq instead of config space >>> >>> Thanks >> >> Another thing if we want to go this way: >> >> We need find a way to terminate the data path from the kernel side, to >> implement to reset semantic. >> > Do you mean terminate the data path in vdpa_reset(). Yes. > Is it ok to just > notify userspace to stop data path asynchronously? For well-behaved userspace, yes but no for buggy or malicious ones. I had an idea, how about terminate IOTLB in this case? Then we're in fact turn datapath off. Thanks > Userspace should > not be able to do any I/O at that time because the iotlb mapping is > already removed. > > Thanks, > Yongji >