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 C2AC4C4708C for ; Thu, 27 May 2021 08:41:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A12B9613CA for ; Thu, 27 May 2021 08:41:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235525AbhE0Im5 (ORCPT ); Thu, 27 May 2021 04:42:57 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:35044 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235284AbhE0Imy (ORCPT ); Thu, 27 May 2021 04:42:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622104877; 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=yN1LmC6tLlwHE2JSmI5/WtXdvMUbtIRH+V/hkQT9TzA=; b=JHr2dwA3m2wYjgaiPOSQfPpwDC+2/4Kn0W3j/E/U/xkC//oJoDjRUEufaik8zryPnbVqud VKJoyzyamPL8qu1XV9EQZIF1HIKZoNhwYYZl7/Vaja4vLyA24C0aeAtGJm+FMkXi0zljyA Y5e031OIUryvuOalYF1tg/hwv8fELw4= Received: from mail-pg1-f199.google.com (mail-pg1-f199.google.com [209.85.215.199]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-587-ntt6xPNxPf6xy9jX_JOrdw-1; Thu, 27 May 2021 04:41:15 -0400 X-MC-Unique: ntt6xPNxPf6xy9jX_JOrdw-1 Received: by mail-pg1-f199.google.com with SMTP id v12-20020a63d54c0000b02902167d3d2f08so2515699pgi.13 for ; Thu, 27 May 2021 01:41:15 -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=yN1LmC6tLlwHE2JSmI5/WtXdvMUbtIRH+V/hkQT9TzA=; b=WkKdqd9D+71cRs/U6lynGyi5Uo2bKMoN3xDmlxgHLqKz0uNIxnrdmkMa7sEXZ47AAW /eQeDSMmxrrRVkbV7qe3NzSB4fQFw+T2fMOd9snckEWzxEwnThaMCuNisN87vPk6Az1M zbHw1q2A1iQpm7+aoDM35s8Ts6KRP1NIBpBEBk4EsmLQpdkBeeS7E3oxN03bKq0zruLZ ih61PvjH5lwzuB/SO711jmuo/EALc9RmW7IJMOuU3iyyhswOJCxLg8h8euetubX04x+V FUJcdSkViF9B/tNSbRsY74WQx3sj5EpXdM3zMMoAONbfRdpYU/e6IHO8OlBU2V6V+FpC oByg== X-Gm-Message-State: AOAM532AqJR8G8HDTckElUJ/pCmdAAzjUE4zU9UADcT1hD0i1sG6JFu0 dFsrYb2AnM3RQ47b4V/VKmSgsqWt7QkY5a8VB+fbhfuV2YVKfTugiyJtZAMcapymd9VgDKase1+ nQVp/UjoTQFkIMACs X-Received: by 2002:a17:902:d508:b029:ef:b008:f4ad with SMTP id b8-20020a170902d508b02900efb008f4admr2333588plg.8.1622104874603; Thu, 27 May 2021 01:41:14 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzvPNDcYkAS3faf7fevSyiFC8ZU6oTJ+el34W9W0mGRDdwfnLELCNOSU91eRydTJVumJh4SSA== X-Received: by 2002:a17:902:d508:b029:ef:b008:f4ad with SMTP id b8-20020a170902d508b02900efb008f4admr2333565plg.8.1622104874245; Thu, 27 May 2021 01:41:14 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id a12sm1513042pfg.102.2021.05.27.01.41.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 May 2021 01:41:13 -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> From: Jason Wang Message-ID: <00ded99f-91b6-ba92-5d92-2366b163f129@redhat.com> Date: Thu, 27 May 2021 16:41:01 +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: netdev@vger.kernel.org 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 > > Thanks, > Yongji >