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Mon, 27 Jul 2020 12:10:42 +0000 From: Wei Hu To: Lorenzo Pieralisi CC: KY Srinivasan , Haiyang Zhang , Stephen Hemminger , "wei.liu@kernel.org" , "robh@kernel.org" , "bhelgaas@google.com" , "linux-hyperv@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Dexuan Cui , Michael Kelley Subject: RE: [PATCH v4] PCI: hv: Fix a timing issue which causes kdump to fail occasionally Thread-Topic: [PATCH v4] PCI: hv: Fix a timing issue which causes kdump to fail occasionally Thread-Index: AQHWY+YSLxC8RPb4v0CKay4JYMaVmKkbR54AgAAKXVA= Date: Mon, 27 Jul 2020 12:10:40 +0000 Message-ID: References: <20200727071731.18516-1-weh@microsoft.com> <20200727111852.GA14239@e121166-lin.cambridge.arm.com> In-Reply-To: <20200727111852.GA14239@e121166-lin.cambridge.arm.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=true; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SetDate=2020-07-27T12:10:39Z; 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x-ms-exchange-antispam-messagedata: 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SG2P153MB0377.APCP153.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-Network-Message-Id: 0c7eaae1-e706-46dc-d163-08d8322615a3 X-MS-Exchange-CrossTenant-originalarrivaltime: 27 Jul 2020 12:10:40.9999 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: cKxpgekG98P5zT6QSSnM4ZugRWO0yx3TyVZWqQyIY/pJqxhbcbzDUGcNe9woku9aRyALOrW2xaJIxni711hWBQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SG2P153MB0379 Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org > -----Original Message----- > From: Lorenzo Pieralisi > Sent: Monday, July 27, 2020 7:19 PM > To: Wei Hu > Cc: KY Srinivasan ; Haiyang Zhang > ; Stephen Hemminger ; > wei.liu@kernel.org; robh@kernel.org; bhelgaas@google.com; linux- > hyperv@vger.kernel.org; linux-pci@vger.kernel.org; linux- > kernel@vger.kernel.org; Dexuan Cui ; Michael Kelley > > Subject: Re: [PATCH v4] PCI: hv: Fix a timing issue which causes kdump to= fail > occasionally >=20 > On Mon, Jul 27, 2020 at 03:17:31PM +0800, Wei Hu wrote: > > Kdump could fail sometime on Hyper-V guest over Accelerated Network > > interface. This is because the retry in hv_pci_enter_d0() releases > > child device strurctures in hv_pci_bus_exit(). Although there is a > > second asynchronous device relations message sending from the host, if > > this message arrives guest after hv_send_resource_allocated() is > > called, the retry would fail. > > > > Fix the problem by moving retry to hv_pci_probe() and starting retry > > from hv_pci_query_relations() call. This will cause a device > > relations message to arrive guest synchronously. The guest would be > > able to rebuild the child device structures before calling > > hv_send_resource_allocated(). > > > > This problem only happens on Accelerated Network or SRIOV devices as > > only such devices currently are attached under vmbus PCI bridge. > > > > Fixes: c81992e7f4aa ("PCI: hv: Retry PCI bus D0 entry on invalid > > device state") > > Signed-off-by: Wei Hu > > Reviewed-by: Michael Kelley > > --- > > v2: Adding Fixes tag according to Michael Kelley's review comment. > > v3: Fix couple typos and reword commit message to make it clearer. > > Thanks the comments from Bjorn Helgaas. > > v4: Adding more problem descritpions in the commit message > > and code upon request from Lorenze Pieralisi. > > > > drivers/pci/controller/pci-hyperv.c | 71 > > +++++++++++++++-------------- > > 1 file changed, 37 insertions(+), 34 deletions(-) > > > > diff --git a/drivers/pci/controller/pci-hyperv.c > > b/drivers/pci/controller/pci-hyperv.c >=20 > I edited commit log and a comment in the code to fix a typo and pushed ou= t to > pci/hv. >=20 > Thanks, > Lorenzo >=20 Thanks Lorenzo. Appreciate your helps! Wei