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Biederman" CC: Konrad Rzeszutek Wilk , Dave Young , Andrew Morton , "bhe@redhat.com" , "linux-kernel@vger.kernel.org" , "kexec@lists.infradead.org" , Eric DeVolder , Boris Ostrovsky , Tianyu Lan , Wei Liu , Masami Hiramatsu , HATAYAMA Daisuke Subject: RE: [PATCH] Only allow to set crash_kexec_post_notifiers on boot time Thread-Topic: [PATCH] Only allow to set crash_kexec_post_notifiers on boot time Thread-Index: AQHWjWt1j9ACvI5nEEKX++S5B3a5m6lvIiCAgARrsQCAAGirnIABlVCAgADbToCAAZcR8IAABdcsgAAARZA= Date: Thu, 24 Sep 2020 16:43:03 +0000 Message-ID: References: <20200918032546.GA4180@dhcp-128-65.nay.redhat.com> <20200918174743.0994c59f058451948837dcb6@linux-foundation.org> <20200921201811.GB3437@char.us.oracle.com> <87v9g6fuub.fsf@x220.int.ebiederm.org> <20200923024329.GB3642@dhcp-128-65.nay.redhat.com> <20200923154825.GC7635@char.us.oracle.com> <874knndtvo.fsf@x220.int.ebiederm.org> In-Reply-To: <874knndtvo.fsf@x220.int.ebiederm.org> 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=2020-09-24T16:43:01Z; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Method=Standard; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Name=Internal; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ActionId=ddc6a247-4359-4955-8272-cbd192be8f04; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ContentBits=0 authentication-results: xmission.com; dkim=none (message not signed) header.d=none;xmission.com; dmarc=none action=none header.from=microsoft.com; x-originating-ip: [24.22.167.197] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 5b1fb6c0-1445-4271-8141-08d860a8e7fe x-ms-traffictypediagnostic: MWHPR21MB0144: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:1923; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: JHPWKbqIaK3AJPaBXSf2wprIB6mpYx7fzXm2K9qsXzmJmg1CWx7aVnX4m9JykMr0HQvvxGtCoTFWOwpP1pDmxax+XEGBee732c8AtOsnYlS/f9H18TNhsHAVlDPosJIG7NadYAFtWGsvcC8K8agez8ohNK00rZpogQ4Wv8nhnLQpuIPfJ3aMQyJp5mpJDOurTXn8QMpakpAxaw3s70BpFX+x/tnet+eeSdHyvXmGLXD35VazgglOzQ/0qYWJ+oa8KOhBwp1vCt4mr58xwfKq5hROA8hhT+s+/Aw955Pmaqqb3W6w+z8KCLJ6pH0f1R+0LZoAZnk4w3jHRY/lk110i0Udwew8dzvXftBt/hUBa3Gjsru8tPyoPDDObMJJZBaa x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MW2PR2101MB1052.namprd21.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(346002)(376002)(396003)(136003)(366004)(39860400002)(186003)(6506007)(8676002)(6916009)(76116006)(5660300002)(26005)(478600001)(82950400001)(82960400001)(54906003)(86362001)(316002)(66946007)(71200400001)(10290500003)(66556008)(8936002)(7696005)(66446008)(83380400001)(7416002)(33656002)(8990500004)(52536014)(4326008)(2906002)(55016002)(9686003)(66476007)(64756008);DIR:OUT;SFP:1102; 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: MW2PR2101MB1052.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5b1fb6c0-1445-4271-8141-08d860a8e7fe X-MS-Exchange-CrossTenant-originalarrivaltime: 24 Sep 2020 16:43:03.4074 (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: JMRhWzvN/AKHYNqs+SVYhrhWqK6MFgfZd+jt+hwYdH27oF4R3lKFBcbzkNVWm+98+cRu7AhFl90qd9fNafMy7Zgh3Vfp4JxwNvMDP5nnI+A= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR21MB0144 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric W. Biederman Sent: Thursday, September 2= 4, 2020 9:26 AM >=20 > Michael Kelley writes: >=20 > >> > > >> > Added Hyper-V people and people who created the param, it is below > >> > commit, I also want to remove it if possible, let's see how people > >> > think, but the least way should be to disable the auto setting in bo= th systemd > >> > and kernel: > > > > Hyper-V uses a notifier to inform the host system that a Linux VM has > > panic'ed. Informing the host is particularly important in a public clo= ud > > such as Azure so that the cloud software can alert the customer, and ca= n > > track cloud-wide reliability statistics. Whether a kdump is taken is = controlled > > entirely by the customer and how he configures the VM, and we want > > the host to be informed either way. >=20 > Why? >=20 > Why does the host care? > Especially if the VM continues executing into a kdump kernel? The host itself doesn't care. But the host is a convenient out-of-band channel for recording that a panic has occurred and to collect basic data about the panic. This out-of-band channel is then used to notify the end customer that his VM has panic'ed. Sure, the customer should be running his own monitoring software, but customers don't always do what they should. Equally important, the out-of-band channel allows the cloud infrastructure software to notice trends, such as that the rate of Linux panics has increased, and that perhaps there is a cloud problem that should be investigated. >=20 > Further like I have mentioned everytime something like this has come up > a call on the kexec on panic code path should be a direct call (That can > be audited) not something hidden in a notifier call chain (which can not)= . >=20 The use case I describe has no particular requirement that it be implemented via the notifier call chain. If there's a better way to run some out-of-band notification code on all Linux panics regardless of whether a kdump is taken, we're open to such an alternative. Michael