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 DD6C1C04A68 for ; Thu, 28 Jul 2022 11:47:01 +0000 (UTC) Received: from localhost ([::1]:33880 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oH1ym-00016W-Gd for qemu-devel@archiver.kernel.org; Thu, 28 Jul 2022 07:47:00 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35668) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oH1tE-0007kI-IL for qemu-devel@nongnu.org; Thu, 28 Jul 2022 07:41:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:44649) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oH1tA-00044d-6y for qemu-devel@nongnu.org; Thu, 28 Jul 2022 07:41:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659008471; 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=enSnMpvaX+527zoW/ahjBvCEO8NqpsHdhMh9TXPIKmY=; b=aL1QtdkuGLbT2YOXwCMXX73T+/9d4Qr+nd109Fti1Rra+nQ43vV6H0gWv/3khSJ8L07ZKe 1VCmFmo321O67pF15f672qqov2pphOI2i4ZonUYaXbQHLgywLP5L4YE5YT/OGvcXW7P3U+ T1L4Er0mbSRjcOf2zz4TSlowb6mMX0Y= Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-612-hnsnCU65NBiXmoJ0px37DA-1; Thu, 28 Jul 2022 07:41:10 -0400 X-MC-Unique: hnsnCU65NBiXmoJ0px37DA-1 Received: by mail-ed1-f71.google.com with SMTP id n8-20020a05640205c800b00434fb0c150cso919993edx.19 for ; Thu, 28 Jul 2022 04:41:10 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc; bh=enSnMpvaX+527zoW/ahjBvCEO8NqpsHdhMh9TXPIKmY=; b=y5GpvhZZfjtApv1WUrogrY/NL6b5gDwwiiFCehV9jKHHD1bwUbotif4qIhrU5ADc1U gUTF3V9dMY/BINGS1FPIjtUydt1mYy2Zb8YvfUFaCCCFrM159Yp3oJ1Hrvy9iWXrdmm6 nL1bqy1fR92+BhM9Oxx7/gQ8QWAmeuaFbB5dkPDm+Frht424PL5kuRu6kf597WbWwjMA CYZQjcg/EznKHyUnapqty8h82IykxVnS8QFZ76NWpl8Sbkx0bMaeWaAL8ZSKLbotemNu kS9TNHmAwhgd7v8rXi7GIpCYRghc/ISsofQdu0RzuE3d+AUCToNHzJCi/m2aDidRpKQr kcZA== X-Gm-Message-State: AJIora/INQLrZpuqfZn7ZeEk/oADVFtUdZ/R0/URqi8Jw8RE7YvEa5EV 33gk+nUXnD8vkbzKeB3m1SmCSqvOqXEicYKOuINV/qHIy3o4r2WdqBv+WQuaTwOdvPpRbht/JIa pMlcJLcjzdm1EafY= X-Received: by 2002:a05:6402:5249:b0:43c:cb3e:d7f8 with SMTP id t9-20020a056402524900b0043ccb3ed7f8mr5095705edd.56.1659008469019; Thu, 28 Jul 2022 04:41:09 -0700 (PDT) X-Google-Smtp-Source: AGRyM1urxyvEYEf6YdKG/X0gshL9UuEwa/RIZEtMlewlCkzZHYANIkNn2ItN7LMnAsSyjBkCAj+iVg== X-Received: by 2002:a05:6402:5249:b0:43c:cb3e:d7f8 with SMTP id t9-20020a056402524900b0043ccb3ed7f8mr5095674edd.56.1659008468468; Thu, 28 Jul 2022 04:41:08 -0700 (PDT) Received: from redhat.com ([2.54.183.236]) by smtp.gmail.com with ESMTPSA id q15-20020a17090676cf00b006fed93bf71fsm342124ejn.18.2022.07.28.04.41.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Jul 2022 04:41:07 -0700 (PDT) Date: Thu, 28 Jul 2022 07:41:04 -0400 From: "Michael S. Tsirkin" To: Claudio Fontana Cc: Jason Wang , qemu-devel , Alex =?iso-8859-1?Q?Benn=E9e?= , Marcel Apfelbaum Subject: Re: virtio: why no full reset on virtio_set_status 0 ? Message-ID: <20220728073757-mutt-send-email-mst@kernel.org> References: <8350fff5-f8d7-11a4-9f3a-aac8b7f5a964@suse.de> <20220727112737-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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" On Thu, Jul 28, 2022 at 09:43:56AM +0200, Claudio Fontana wrote: > On 7/28/22 03:27, Jason Wang wrote: > > On Wed, Jul 27, 2022 at 11:32 PM Michael S. Tsirkin wrote: > >> > >> On Wed, Jul 27, 2022 at 12:51:31PM +0200, Claudio Fontana wrote: > >>> Hi Michael and all, > >>> > >>> I have started researching a qemu / ovs / dpdk bug: > >>> > >>> https://inbox.dpdk.org/dev/322122fb-619d-96f6-5c3e-9eabdbf3819a@redhat.com/T/ > >>> > >>> that seems to be affecting multiple parties in the telco space, > >>> > >>> and during this process I noticed that qemu/hw/virtio/virtio.c does not do a full virtio reset > >>> in virtio_set_status, when receiving a status value of 0. > >>> > >>> It seems it has always been this way, so I am clearly missing / forgetting something basic, > >>> > >>> I checked the virtio spec at https://docs.oasis-open.org/ > >>> > >>> and from: > >>> > >>> " > >>> 4.1.4.3 Common configuration structure layout > >>> > >>> device_status > >>> The driver writes the device status here (see 2.1). Writing 0 into this field resets the device. > >>> > >>> " > >>> > >>> and > >>> > >>> " > >>> 2.4.1 Device Requirements: Device Reset > >>> A device MUST reinitialize device status to 0 after receiving a reset. > >>> " > >>> > >>> I would conclude that in virtio.c::virtio_set_status we should unconditionally do a full virtio_reset. > >>> > >>> Instead, we have just the check: > >>> > >>> if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) != > >>> (val & VIRTIO_CONFIG_S_DRIVER_OK)) { > >>> virtio_set_started(vdev, val & VIRTIO_CONFIG_S_DRIVER_OK); > >>> } > >>> > >>> which just sets the started field, > >>> > >>> and then we have the call to the virtio device class set_status (virtio_net...), > >>> but the VirtioDevice is not fully reset, as per the virtio_reset() call we are missing: > >>> > >>> " > >>> vdev->start_on_kick = false; > >>> vdev->started = false; > >>> vdev->broken = false; > >>> vdev->guest_features = 0; > >>> vdev->queue_sel = 0; > >>> vdev->status = 0; > >>> vdev->disabled = false; > >>> qatomic_set(&vdev->isr, 0); > >>> vdev->config_vector = VIRTIO_NO_VECTOR; > >>> virtio_notify_vector(vdev, vdev->config_vector); > >>> > >>> for(i = 0; i < VIRTIO_QUEUE_MAX; i++) { > >>> ... initialize vdev->vq[i] ... > >>> } > >>> " > >>> > >>> Doing a full reset seems to fix the problem for me, so I can send tentative patches if necessary, > >>> but what am I missing here? > >>> > >>> Thanks, > >>> > >>> Claudio > >>> > >>> -- > >>> Claudio Fontana > >>> Engineering Manager Virtualization, SUSE Labs Core > >>> > >>> SUSE Software Solutions Italy Srl > >> > >> > >> So for example for pci: > >> > >> case VIRTIO_PCI_STATUS: > >> > >> > >> .... > >> > >> if (vdev->status == 0) { > >> virtio_pci_reset(DEVICE(proxy)); > >> } > >> > >> which I suspect is a bug because: > >> > >> static void virtio_pci_reset(DeviceState *qdev) > >> { > >> VirtIOPCIProxy *proxy = VIRTIO_PCI(qdev); > >> VirtioBusState *bus = VIRTIO_BUS(&proxy->bus); > >> PCIDevice *dev = PCI_DEVICE(qdev); > >> int i; > >> > >> virtio_bus_reset(bus); > > > > Note that we do virtio_reset() here. > > > Yes, thank you, I completely overlooked it, I noticed this in Michael's response as well. > > However we end up with multiple calls to k->set_status, one from the virtio_set_status call, > and one from the virtio_bus_reset(), which is probably something we don't want. > > All in all it is not clear what the meaning of virtio_set_status is supposed to be I think, > and I wonder what the assumptions are among all the callers. > If it is supposed to be an implementation of the virtio standard field as described, I think we should do the reset right then and there, > but maybe the true meaning of the function is another one I couldn't understand, since _some_ of the cases are processes there. > > And there is a question about ordering: > > in virtio_pci we end up calling virtio_set_status(0), which gets us k->set_status(vdev, 0), which lands in virtio_net_set_status(0) and virtio_net_vhost_status, > which causes a vhost_net_stop(). > Should we instead land in virtio_net_reset() first, by doing a virtio reset earlier when detecting a 0 value from the driver? Well we want to first stop the backend and only then reset our local state. Seems to make sense ... > in the scenario I am looking at (with vhost-user, ovs/dpdk, and a guest testpmd application), > the guest application goes away without any chance to signal (kill -9), then gets immediately restarted and does a write of 0 to status, while qemu and ovs still hold the state for the device. > > As QEMU lands in vhost_net_stop(), it seems to cause a chain of events that crash ovs which is trying to read an rx burst from the queue, Not sure I got this part. > while QEMU is left hanging waiting forever for a response to VHOST_USER_GET_VRING_BASE issued as a result of vhost_net_stop. Ineteresting why doesn't socket close after ovs crash cause the read to fail. > Just saying, I am having more success with the second ordering, but I am still studying, don't have the full picture yet. > > Thanks, > > Claudio > > > > >> msix_unuse_all_vectors(&proxy->pci_dev); > >> > >> for (i = 0; i < VIRTIO_QUEUE_MAX; i++) { > >> proxy->vqs[i].enabled = 0; > >> proxy->vqs[i].num = 0; > >> proxy->vqs[i].desc[0] = proxy->vqs[i].desc[1] = 0; > >> proxy->vqs[i].avail[0] = proxy->vqs[i].avail[1] = 0; > >> proxy->vqs[i].used[0] = proxy->vqs[i].used[1] = 0; > >> } > >> > >> > >> so far so good > >> > >> if (pci_is_express(dev)) { > >> pcie_cap_deverr_reset(dev); > >> pcie_cap_lnkctl_reset(dev); > >> > >> pci_set_word(dev->config + dev->exp.pm_cap + PCI_PM_CTRL, 0); > >> } > >> > >> this part is wrong I think, it got here by mistake since the same > >> function is used for bus level reset. > >> > >> Jason, Marcel, any input? > > > > Yes, I think we don't need PCI stuff here. We do virtio reset not pci. > > > > Thanks > > > >> > >> -- > >> MST > >> > > > >