Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Dexuan Cui <decui@microsoft.com>
To:     'Lorenzo Pieralisi' <lorenzo.pieralisi@arm.com>
CC:     "'bhelgaas@google.com'" <bhelgaas@google.com>,
        "'linux-pci@vger.kernel.org'" <linux-pci@vger.kernel.org>,
        KY Srinivasan <kys@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>,
        "'driverdev-devel@linuxdriverproject.org'" 
        <driverdev-devel@linuxdriverproject.org>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "'olaf@aepfle.de'" <olaf@aepfle.de>,
        "'apw@canonical.com'" <apw@canonical.com>,
        "'jasowang@redhat.com'" <jasowang@redhat.com>,
        "'vkuznets@redhat.com'" <vkuznets@redhat.com>,
        "'marcelo.cerri@canonical.com'" <marcelo.cerri@canonical.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Subject: RE: [PATCH v4 1/2] PCI: hv: Serialize the present and eject work
 items
Thread-Topic: [PATCH v4 1/2] PCI: hv: Serialize the present and eject work
 items
Thread-Index: AdO8O3aRSVmxMVp3Qwu6AztIm4xINgAQ81WAAAFLJ6AAATH/AA==
Date:   Thu, 15 Mar 2018 18:28:21 +0000
Message-ID: <KL1P15301MB00065FB13CC4AFC4C64DFBB3BFD00@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM>
References: <KL1P15301MB0006C96F94181FFB93A222D8BFD00@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM>
 <20180315170131.GA22134@e107981-ln.cambridge.arm.com>
 <KL1P15301MB00064712309002FB85341ACDBFD00@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM>
In-Reply-To: <KL1P15301MB00064712309002FB85341ACDBFD00@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM>
Accept-Language: en-US
Content-Language: en-US
msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=True;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Owner=decui@microsoft.com;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SetDate=2018-03-15T17:55:01.7168159Z;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Name=General;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Application=Microsoft Azure
 Information Protection;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Extended_MSFT_Method=Automatic;
 Sensitivity=General
authentication-results: spf=none (sender IP is )
 smtp.mailfrom=decui@microsoft.com; 
x-originating-ip: [2001:4898:80e8::39a]
x-ms-publictraffictype: Email
x-microsoft-exchange-diagnostics: 1;KL1P15301MB0055;7:gjSrlPJ17AQwEqHx6/HAe6rEr8mTplsQMA0DBhCKVZYNtd+jDKUdM3XxmGDb0J2l3N/AexVRBMeTuD0Jco5wK4lUFkoKSLnBPs79WqprnNcCXs+u/zHtgr5dVQojcDOcShjKcF/cVDrFUegCc4QDChD5Zi4NB1v0HDZRTdC22aVAD2vusLXlglZG1T1WAY3UjVhbHs8YEEr6/j5nC1a36zHtrIYpMMD4WmbFslYUimgHOWwJr6G+242Ld+coUiAR;20:YfxZg93G6EuiW1tk1YC5rca69z1TGZKPtoLujCbSGBO2tN/ryTWtDJBQbRsGg1qbkBGP6FxmNvdO1MHMTIn10PM4iJxAIoILL3UgGXKMKpFCH+vWLQZ3XBxXVGAf/ZqyHDiT+VsfGsjdXUv6yBZ+n/p80bM6DvynQGL7D23QL2g=
x-ms-exchange-antispam-srfa-diagnostics: SSOS;SSOR;
x-ms-office365-filtering-ht: Tenant
x-ms-office365-filtering-correlation-id: 1db45b65-9746-4785-4a3e-08d58aa2883e
x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:KL1P15301MB0055;
x-ms-traffictypediagnostic: KL1P15301MB0055:
x-microsoft-antispam-prvs: <KL1P15301MB00558A79D6AD0D0F30611F50BFD00@KL1P15301MB0055.APCP153.PROD.OUTLOOK.COM>
x-exchange-antispam-report-test: UriScan:(180628864354917)(9452136761055);
x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(8211001083)(61425038)(6040522)(2401047)(8121501046)(5005006)(10201501046)(3231221)(944501244)(52105095)(93006095)(93001095)(3002001)(6055026)(61426038)(61427038)(6041310)(20161123560045)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(20161123558120)(20161123562045)(20161123564045)(6072148)(201708071742011);SRVR:KL1P15301MB0055;BCL:0;PCL:0;RULEID:;SRVR:KL1P15301MB0055;
x-forefront-prvs: 0612E553B4
x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(39380400002)(39860400002)(396003)(366004)(376002)(346002)(199004)(189003)(51234002)(316002)(46003)(53936002)(55016002)(59450400001)(3280700002)(2950100002)(2900100001)(229853002)(102836004)(86612001)(9686003)(8936002)(33656002)(478600001)(7736002)(6246003)(6506007)(68736007)(107886003)(6916009)(8676002)(74316002)(105586002)(81166006)(5660300001)(10290500003)(25786009)(81156014)(99286004)(14454004)(10090500001)(76176011)(7696005)(186003)(2906002)(4326008)(22452003)(77096007)(86362001)(575784001)(97736004)(8990500004)(3660700001)(6116002)(54906003)(6436002)(2940100002)(106356001)(7416002)(305945005);DIR:OUT;SFP:1102;SCL:1;SRVR:KL1P15301MB0055;H:KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM;FPR:;SPF:None;PTR:InfoNoRecords;A:1;MX:1;LANG:en;
received-spf: None (protection.outlook.com: microsoft.com does not designate
 permitted sender hosts)
x-microsoft-antispam-message-info: kyO+LXhoZciGI1K0NVSKWEGKe3F7KNcnEbNriXKPm9aKQE08c+Nv08ldw3ZzwpKhHHUbMeb8LbeNpBIieTEJTcJleyq8Lgt5PgesLob3eR8NUy12XJrLdMS/xtb4Cg5qjlG53II+QpKEU5rqewTCKJwWDcTyPqwK8eQuNLqu6tpaeWyFeiFfmBr0o8yCkOnyx8Au2z4V5TdaBIWQTxrYR8zRQ2IyC6MXXWAyzrhpFAdi5Y7qjN23CvV9sUEVfMj/DhlxttNqcIoDMtZOicnEudgcv6f2BS97Z/0UGlG4/p2bruIZcPFcZXEFeVuOniPHae4sO1sFFEC0qRLbNatJmQ==
spamdiagnosticoutput: 1:99
spamdiagnosticmetadata: NSPM
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-OriginatorOrg: microsoft.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 1db45b65-9746-4785-4a3e-08d58aa2883e
X-MS-Exchange-CrossTenant-originalarrivaltime: 15 Mar 2018 18:28:21.1974
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47
X-MS-Exchange-Transport-CrossTenantHeadersStamped: KL1P15301MB0055
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

> From: Dexuan Cui
> > From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> > I need to know either what commit you are fixing (ie Fixes: tag - which
> > is preferrable) or you tell me which kernel versions we are targeting
> > for the stable backport.
> > Lorenzo
>=20
> Sorry.  Here I was hesitant to add a "Fixes:" because the bug was there t=
he first
> day
> when the driver was introduced.
>=20
> Please use
> Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsof=
t
> Hyper-V VMs")
> or
> Cc: <stable@vger.kernel.org> # v4.6+

BTW, the bug here is a race condtion which couldn't be easily hit in the pa=
st,
probably because most of the time only one PCI device was only added into t=
he
VM once. But now it's becoming typical that a VM can have 4 GPU devices so =
we
start to notice this bug. With 7 Mellanox VFs assigned to a VM, we can easi=
ly
reproduce the bug by "hot-remove and hot-add VFs" test:

general protection fault: 0000 [#1] SMP
...
Workqueue: events hv_eject_device_work [pci_hyperv]
task: ffff8800ed5e5400 ti: ffff8800ee674000 task.ti: ffff8800ee674000
RIP: 0010:[<ffffffffc025c5ce>]  ... hv_eject_device_work+0xbe/0x160 [pci_hy=
perv]
...
Call Trace:
 [<ffffffff8183c3a6>] ? __schedule+0x3b6/0xa30
 [<ffffffff8109a585>] process_one_work+0x165/0x480
 [<ffffffff8109a8eb>] worker_thread+0x4b/0x4c0
 [<ffffffff8109a8a0>] ? process_one_work+0x480/0x480
 [<ffffffff810a0c25>] kthread+0xe5/0x100
 [<ffffffff810a0b40>] ? kthread_create_on_node+0x1e0/0x1e0
 [<ffffffff81840f0f>] ret_from_fork+0x3f/0x70
 [<ffffffff810a0b40>] ? kthread_create_on_node+0x1e0/0x1e0
Code: ...
RIP  [<ffffffffc025c5ce>] hv_eject_device_work+0xbe/0x160 [pci_hyperv]
...
BUG: unable to handle kernel paging request at ffffffffffffffd8
IP: [<ffffffff810a12d0>] kthread_data+0x10/0x20
PGD 1e0d067 PUD 1e0f067 PMD 0
Oops: 0000 [#2] SMP
=20
Thanks,
-- Dexuan