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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 B5707C2B9F4 for ; Tue, 22 Jun 2021 08:07:46 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 0B98E61353 for ; Tue, 22 Jun 2021 08:07:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0B98E61353 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:39008 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lvbRh-00053y-0h for qemu-devel@archiver.kernel.org; Tue, 22 Jun 2021 04:07:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:37080) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lvbQx-0003lX-W1 for qemu-devel@nongnu.org; Tue, 22 Jun 2021 04:07:00 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:28998) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lvbQV-0001Y4-En for qemu-devel@nongnu.org; Tue, 22 Jun 2021 04:06:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624349188; 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=4Yl/tr0Oc1gVf3AyJaUiecSSGBvDgPag8e+2mSu1GEw=; b=V6Vd+0H2K9zJrDG+T2smcUEaOr7NOVXJevWlXCZtzzeWB4B1nJeK5fnHpt0Vlxc+Rq8Jfz oSSpM9l3aJDaelaJBF1lrgE7EblUXEux+HZ16JlzSqPajEhXrcyhZFHPLN4jdpZUmZZBcz XXA5jpj7BGYuvtf24F5Zt/3k29XhmpA= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-546-LiGS78-HM-m8KHX3x9x-yw-1; Tue, 22 Jun 2021 04:06:25 -0400 X-MC-Unique: LiGS78-HM-m8KHX3x9x-yw-1 Received: by mail-wm1-f70.google.com with SMTP id j38-20020a05600c1c26b02901dbf7d18ff8so420568wms.8 for ; Tue, 22 Jun 2021 01:06:25 -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-language :content-transfer-encoding; bh=4Yl/tr0Oc1gVf3AyJaUiecSSGBvDgPag8e+2mSu1GEw=; b=sFKoYeNYHntIT00MlJRvuD38GlRjR+tz2KGLGrzTzbRSMDIWiRhak10oQG/z1PiwB+ AFuV/Lo8Oi8qjNglEBUUNBJoCNNzbnJiJd2pkLU0SHrXotONe1RxHcLhDPs14SQ3rmOK wLzowMTJqHn+edCSkSYKoQSNxWnlEMC8tHT3iErJhgCUZf9bo6Mu5sw3cNVvHq7Js54i podMyzEFAUGHpeXM1ZgTtz+rJmRdHvpSbYwPzO/i7VDV85rrAvCDfREDyk7vRKvQweV7 c+4mn+g0+FlbuyZeO2boUxoD3WGy+U7jcnKjpfa2pD0mrs9Dmv784JvcrV6SPFTjt2aU 7p/g== X-Gm-Message-State: AOAM533GRIf/8zRbIOUkCiIaVen9E7EWtdO3yorgXC31dI9xhXh0PuoJ inLwBUk3UwpLfHsvT/ACv6QSgbA2s0bUSEI7+BSsxJBqj0427qUf6vcIM//s/eb0U9Uh5KPki2v AJ8kiX5rdl3aGWdg= X-Received: by 2002:a05:600c:1c27:: with SMTP id j39mr2871352wms.139.1624349184120; Tue, 22 Jun 2021 01:06:24 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwSKWYM2WOibF2Hekx3saiq/5GR4uvAjjJN0sUFT1UYW83pX9VIYRzxWp5OK8RqXkqB8/WOZw== X-Received: by 2002:a05:600c:1c27:: with SMTP id j39mr2871315wms.139.1624349183764; Tue, 22 Jun 2021 01:06:23 -0700 (PDT) Received: from [192.168.1.36] (93.red-83-35-24.dynamicip.rima-tde.net. [83.35.24.93]) by smtp.gmail.com with ESMTPSA id v22sm1432114wmh.40.2021.06.22.01.06.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Jun 2021 01:06:23 -0700 (PDT) Subject: Re: [PATCH v2] block/nvme: Fix VFIO_MAP_DMA failed: No space left on device From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= To: Fam Zheng References: <20210621093240.4170701-1-philmd@redhat.com> <9A674DF3-041E-4E7C-BB49-481AA77B1F7B@euphon.net> <6b77db0c-8625-992e-8546-15b9a24ae928@redhat.com> <0EF3A65E-39CB-4114-8572-001C2DF05863@euphon.net> Message-ID: <30f81ba5-cd6a-faee-328d-8ccb8ef76202@redhat.com> Date: Tue, 22 Jun 2021 10:06:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.373, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , qemu-block@nongnu.org, qemu-devel@nongnu.org, =?UTF-8?B?TWljaGFsIFByw612b3puw61r?= , qemu-stable@nongnu.org, Maxim Levitsky , Eric Auger , Alex Williamson , Stefan Hajnoczi , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/22/21 9:29 AM, Philippe Mathieu-Daudé wrote: > On 6/21/21 5:36 PM, Fam Zheng wrote: >>> On 21 Jun 2021, at 16:13, Philippe Mathieu-Daudé wrote: >>> On 6/21/21 3:18 PM, Fam Zheng wrote: >>>>> On 21 Jun 2021, at 10:32, Philippe Mathieu-Daudé wrote: >>>>> >>>>> When the NVMe block driver was introduced (see commit bdd6a90a9e5, >>>>> January 2018), Linux VFIO_IOMMU_MAP_DMA ioctl was only returning >>>>> -ENOMEM in case of error. The driver was correctly handling the >>>>> error path to recycle its volatile IOVA mappings. >>>>> >>>>> To fix CVE-2019-3882, Linux commit 492855939bdb ("vfio/type1: Limit >>>>> DMA mappings per container", April 2019) added the -ENOSPC error to >>>>> signal the user exhausted the DMA mappings available for a container. >>>>> >>>>> The block driver started to mis-behave: >>>>> >>>>> qemu-system-x86_64: VFIO_MAP_DMA failed: No space left on device >>>>> (qemu) >>>>> (qemu) info status >>>>> VM status: paused (io-error) >>>>> (qemu) c >>>>> VFIO_MAP_DMA failed: No space left on device >>>>> qemu-system-x86_64: block/block-backend.c:1968: blk_get_aio_context: Assertion `ctx == blk->ctx' failed. >>>> >>>> Hi Phil, >>>> >>>> >>>> The diff looks good to me, but I’m not sure what exactly caused the assertion failure. There is `if (r) { goto fail; }` that handles -ENOSPC before, so it should be treated as a general case. What am I missing? >>> >>> Good catch, ENOSPC ends setting BLOCK_DEVICE_IO_STATUS_NOSPACE >>> -> BLOCK_ERROR_ACTION_STOP, so the VM is paused with DMA mapping >>> exhausted. I don't understand the full "VM resume" path, but this >>> is not what we want (IO_NOSPACE is to warn the operator to add >>> more storage and resume, which is pointless in our case, resuming >>> won't help until we flush the mappings). >>> >>> IIUC what we want is return ENOMEM to set BLOCK_DEVICE_IO_STATUS_FAILED. >> >> I agree with that. It just makes me feel there’s another bug in the resuming code path. Can you get a backtrace? > > It seems the resuming code path bug has been fixed elsewhere: > > (qemu) info status > info status > VM status: paused (io-error) > (qemu) c > c > 2021-06-22T07:27:00.745466Z qemu-system-x86_64: VFIO_MAP_DMA failed: No > space left on device > (qemu) info status > info status > VM status: paused (io-error) > (qemu) c > c > 2021-06-22T07:27:12.458137Z qemu-system-x86_64: VFIO_MAP_DMA failed: No > space left on device > (qemu) c > c > 2021-06-22T07:27:13.439167Z qemu-system-x86_64: VFIO_MAP_DMA failed: No > space left on device > (qemu) c > c > 2021-06-22T07:27:14.272071Z qemu-system-x86_64: VFIO_MAP_DMA failed: No > space left on device > (qemu) > I tested all releases up to v4.1.0 and could not trigger the blk_get_aio_context() assertion. Building using --enable-debug. IIRC Gentoo is more aggressive, so I'll restart using -O2.