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 13F4DC4708A for ; Thu, 27 May 2021 08:43:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E3FF8613CA for ; Thu, 27 May 2021 08:43:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235545AbhE0IpZ (ORCPT ); Thu, 27 May 2021 04:45:25 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:25094 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235532AbhE0IpZ (ORCPT ); Thu, 27 May 2021 04:45:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622105032; 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=Q4kOVJ8GB+3GLW+q/BipT5oGozNfefpPrW2ucSt2yL8=; b=cmYTK/g2nU1oHCGGUF0JJdvZTOgYXiY6qDCb4qgOUTjbau6sIaZBBSaj2kMaIrS5rnKjWv om7eMlnB5ryjRDsNIRlGXhHaQPyPiBEHz2TORpW1bxDnDOhxf5mfKcvPbjeIppXvTTp5C8 eCXhgtXlUeGx4Tvpegho+hl3eOgK5iQ= Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-359-V7WH9srgO0CA1QzZlo4QLQ-1; Thu, 27 May 2021 04:43:50 -0400 X-MC-Unique: V7WH9srgO0CA1QzZlo4QLQ-1 Received: by mail-pl1-f199.google.com with SMTP id l9-20020a1709030049b02900f184d9d878so1975532pla.16 for ; Thu, 27 May 2021 01:43:49 -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:from:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=Q4kOVJ8GB+3GLW+q/BipT5oGozNfefpPrW2ucSt2yL8=; b=VVBvnPVDjkhZek7nveLQiYJa34q6JOv/MP67Q5Iu5pyvy6n94B0EftL0m6UrWZ87/b sLc0GhpFRZrA3U9pTbNWCGtMTsdJ83em4vxzpEYS3DSwuhdUmGRqoBu+ON5HT+gDLDVb onp2r2IhFrL54+p5Tzc8g+Q6uniZwSW/txV5358CyoGoQkldkqgyQuya5NEbAq0Uw+7u Fx7A/0PWzzrFRf2HP2j98nbHK1VoK/xOPsDmnc49buSNIkWGPOp/pkzh/0f4z0TyzYoG l3gZUJ01+eGvmXp41YlQTARKhMBM3Ku/nogTIo+GOw6+jGLC5DaXaWFij4C4KRegbMrO gqgw== X-Gm-Message-State: AOAM530f1JNO7vLiXfalBIXhcDs8c2G4mqL1CPG5T6lAHpPTSo9MDXgh TR9Vfk7jV5e8svMqbamRpCQ52QgGzDDDGz6wSZl4TaP5qn4W1zAo8oQ9b6WAynHL1SR9duWEbdZ fSaBA0Ll7i8XU3n82eiE/q226bw== X-Received: by 2002:a17:902:aa42:b029:ee:f55a:b2c1 with SMTP id c2-20020a170902aa42b02900eef55ab2c1mr2283377plr.15.1622105028986; Thu, 27 May 2021 01:43:48 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxSObctLvNp4FosLHglZe975VrI39ki5xw8bXJ8rCFLiK5AHUwDmp+dxI3a8RKS9e1DfhzunA== X-Received: by 2002:a17:902:aa42:b029:ee:f55a:b2c1 with SMTP id c2-20020a170902aa42b02900eef55ab2c1mr2283358plr.15.1622105028736; Thu, 27 May 2021 01:43:48 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id e29sm1364517pfm.110.2021.05.27.01.43.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 May 2021 01:43:48 -0700 (PDT) Subject: Re: [PATCH v7 11/12] vduse: Introduce VDUSE - vDPA Device in Userspace From: Jason Wang 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> Message-ID: <3cc7407d-9637-227e-9afa-402b6894d8ac@redhat.com> Date: Thu, 27 May 2021 16:43:40 +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: <00ded99f-91b6-ba92-5d92-2366b163f129@redhat.com> 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. Thanks > > >> >> Thanks, >> Yongji >>