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[23.128.96.18]) by mx.google.com with ESMTP id u10si6362ejx.142.2020.09.24.09.28.34; Thu, 24 Sep 2020 09:28:57 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=xmission.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727010AbgIXQ0K (ORCPT + 99 others); Thu, 24 Sep 2020 12:26:10 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:57004 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726645AbgIXQ0K (ORCPT ); Thu, 24 Sep 2020 12:26:10 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out03.mta.xmission.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1kLU4L-00ENPr-R1; Thu, 24 Sep 2020 10:26:05 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95]:40828 helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1kLU4K-0000tJ-La; Thu, 24 Sep 2020 10:26:05 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Michael Kelley 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 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> Date: Thu, 24 Sep 2020 11:25:31 -0500 In-Reply-To: (Michael Kelley's message of "Thu, 24 Sep 2020 16:15:03 +0000") Message-ID: <874knndtvo.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1kLU4K-0000tJ-La;;;mid=<874knndtvo.fsf@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18JVMPiun/wIfdY3BUVFG/zMkK+3mTcQDU= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa07.xmission.com X-Spam-Level: X-Spam-Status: No, score=0.4 required=8.0 tests=ALL_TRUSTED,BAYES_20, DCC_CHECK_NEGATIVE,LH_URI_DOM_IN_PATH,T_TM2_M_HEADER_IN_MSG, XMGappySubj_01,XMSubLong,XM_B_SpammyWords autolearn=disabled version=3.4.2 X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * -0.0 BAYES_20 BODY: Bayes spam probability is 5 to 20% * [score: 0.0948] * 0.7 XMSubLong Long Subject * 0.5 XMGappySubj_01 Very gappy subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 0.0 LH_URI_DOM_IN_PATH URI: Long-host URI having a domain name in * the path part * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.2 XM_B_SpammyWords One or more commonly used spammy words X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Michael Kelley X-Spam-Relay-Country: X-Spam-Timing: total 608 ms - load_scoreonly_sql: 0.04 (0.0%), signal_user_changed: 11 (1.7%), b_tie_ro: 9 (1.5%), parse: 0.91 (0.1%), extract_message_metadata: 5 (0.9%), get_uri_detail_list: 3.3 (0.5%), tests_pri_-1000: 3.9 (0.6%), tests_pri_-950: 1.26 (0.2%), tests_pri_-900: 1.01 (0.2%), tests_pri_-90: 200 (32.9%), check_bayes: 198 (32.5%), b_tokenize: 11 (1.9%), b_tok_get_all: 11 (1.8%), b_comp_prob: 3.9 (0.6%), b_tok_touch_all: 166 (27.3%), b_finish: 1.08 (0.2%), tests_pri_0: 364 (59.8%), check_dkim_signature: 0.57 (0.1%), check_dkim_adsp: 3.4 (0.6%), poll_dns_idle: 1.01 (0.2%), tests_pri_10: 2.5 (0.4%), tests_pri_500: 12 (1.9%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH] Only allow to set crash_kexec_post_notifiers on boot time X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michael Kelley writes: > From: Konrad Rzeszutek Wilk Sent: Wednesday, September 23, 2020 8:48 AM >> >> On Wed, Sep 23, 2020 at 10:43:29AM +0800, Dave Young wrote: >> > + more people who may care about this param >> >> Paarty time!! >> >> (See below, didn't snip any comments) >> > On 09/21/20 at 08:45pm, Eric W. Biederman wrote: >> > > Konrad Rzeszutek Wilk writes: >> > > >> > > > On Fri, Sep 18, 2020 at 05:47:43PM -0700, Andrew Morton wrote: >> > > >> On Fri, 18 Sep 2020 11:25:46 +0800 Dave Young wrote: >> > > >> >> > > >> > crash_kexec_post_notifiers enables running various panic notifier >> > > >> > before kdump kernel booting. This increases risks of kdump failure. >> > > >> > It is well documented in kernel-parameters.txt. We do not suggest >> > > >> > people to enable it together with kdump unless he/she is really sure. >> > > >> > This is also not suggested to be enabled by default when users are >> > > >> > not aware in distributions. >> > > >> > >> > > >> > But unfortunately it is enabled by default in systemd, see below >> > > >> > discussions in a systemd report, we can not convince systemd to change >> > > >> > it: >> > > >> > >> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fsyst >> emd%2Fsystemd%2Fissues%2F16661&data=02%7C01%7Cmikelley%40microsoft.com% >> 7C3631bae06f7147c0f92908d85fd7f2b2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0% >> 7C637364728378052956&sdata=9CUpPUxcKLLggbJ1bjubBjbFUAhPVeZhIc4yss8wAiU%3 >> D&reserved=0 >> > > >> > >> > > >> > Actually we have got reports about kdump kernel hangs in both s390x >> > > >> > and powerpcle cases caused by the systemd change, also some x86 cases >> > > >> > could also be caused by the same (although that is in Hyper-V code >> > > >> > instead of systemd, that need to be addressed separately). >> > > > >> > > > Perhaps it may be better to fix the issus on s390x and PowerPC as well? >> > > > >> > > >> > >> > > >> > Thus to avoid the auto enablement here just disable the param writable >> > > >> > permission in sysfs. >> > > >> > >> > > >> >> > > >> Well. I don't think this is at all a desirable way of resolving a >> > > >> disagreement with the systemd developers >> > > >> >> > > >> At the above github address I'm seeing "ryncsn added a commit to >> > > >> ryncsn/systemd that referenced this issue 9 days ago", "pstore: don't >> > > >> enable crash_kexec_post_notifiers by default". So didn't that address >> > > >> the issue? >> > > > >> > > > It does in systemd, but there is a strong interest in making this on >> > > > by default. >> > > >> > > There is also a strong interest in removing this code entirely from the >> > > kernel. >> > >> > 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 both 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 cloud > such as Azure so that the cloud software can alert the customer, and can > 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. Why? Why does the host care? Especially if the VM continues executing into a kdump kernel? 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). Eric