From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Date: Thu, 1 Oct 2015 08:27:33 +0200 From: Peter Zijlstra Subject: Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Message-ID: <20151001062733.GL2881@worktop.programming.kicks-ass.net> References: <20150925112803.4258.94241.stgit@softrs> <20150925112811.4258.54494.stgit@softrs> <20150930115548.GI2881@worktop.programming.kicks-ass.net> <04EAB7311EE43145B2D3536183D1A8445499CD11@GSjpTKYDCembx31.service.hitachi.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <04EAB7311EE43145B2D3536183D1A8445499CD11@GSjpTKYDCembx31.service.hitachi.net> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: =?utf-8?B?5rKz5ZCI6Iux5a6PIC8gS0FXQUnvvIxISURFSElSTw==?= Cc: "x86@kernel.org" , Jonathan Corbet , "linux-doc@vger.kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Michal Hocko , Ingo Molnar , Thomas Gleixner , "Eric W. Biederman" , "H. Peter Anvin" , =?utf-8?B?5bmz5p2+6ZuF5bezIC8gSElSQU1BVFXvvIxNQVNBTUk=?= , Andrew Morton , Ingo Molnar , Vivek Goyal T24gVGh1LCBPY3QgMDEsIDIwMTUgYXQgMDI6MzM6MThBTSArMDAwMCwg5rKz5ZCI6Iux5a6PIC8g S0FXQUnvvIxISURFSElSTyB3cm90ZToKPiA+IE9uIEZyaSwgU2VwIDI1LCAyMDE1IGF0IDA4OjI4 OjExUE0gKzA5MDAsIEhpZGVoaXJvIEthd2FpIHdyb3RlOgo+ID4gPiBUaGlzIHBhdGNoIGludHJv ZHVjZXMgbmV3IGJvb3Qgb3B0aW9uICJub2V4dG5taSIgd2hpY2ggZGlzYWJsZXMKPiA+ID4gZXh0 ZXJuYWwgTk1JLiAgVGhpcyBvcHRpb24gaXMgdXNlZnVsIGZvciB0aGUgZHVtcCBjYXB0dXJlIGtl cm5lbAo+ID4gPiBzbyB0aGF0IGFuIEhBIGFwcGxpY2F0aW9uIG9yIGFkbWluaXN0cmF0b3Igd291 bGRuJ3QgbWlzdGFrZW5seQo+ID4gPiBzaG9vdCBkb3duIHRoZSBrZXJuZWwgYnkgTk1JLgo+ID4g Cj4gPiBTbyB0aGF0IHRoZXkgY2FuIGdldCByZWFsbHkgc3R1Y2sgd2hlbiB0aGUgY3Jhc2gga2Vy bmVsIGNyYXNoZXMsIHJpZ2h0Pwo+ID4gOy0pCj4gCj4gTm8sIGl0IGlzIGRpZmZlcmVudCBmcm9t IG15IGludGVudGlvbi4KPiAKPiBgbWlzdGFrZW5seScgaW4gdGhlIGFib3ZlIG1lYW5zOyB0aGV5 IGlzc3VlIE5NSSBkdWUgdG8gYSBtaXNjb25jZXB0aW9uCj4gdGhhdCB0aGUgbW9uaXRvcmVkIGhv c3QgaXMgc3R1Y2sgaW4gdGhlIDFzdCBrZXJuZWwgd2hpbGUgaXQgaXMgYWN0dWFsbHkKPiB0YWtp bmcgYSBjcmFzaCBkdW1wIGluIHRoZSAybmQga2VybmVsLiAgVG8gYXZvaWQgdGhpcyBraW5kIG9m IGFjY2lkZW50LAo+IHRoZXJlIGlzIGEgdG9vbCBzdWNoIGFzIGZlbmNlX2tkdW1wIHdoaWNoIG5v dGlmaWVzICJJJ20gdGFraW5nIGEgY3Jhc2gKPiBkdW1wLCBzbyBkb24ndCBzZW5kIE5NSSIgdG8g dGhlIEhBIGNsdXN0ZXJpbmcgc29mdHdhcmUuICBIb3dldmVyLCB0aGVyZQo+IGlzIGEgdGltZSB3 aW5kb3cgYmV0d2VlbiBrZXJuZWwgcGFuaWMgYW5kIHRoZSBub3RpZmljYXRpb24uCj4gCj4gIm5v ZXh0bm1pIiBhbGxvd3MgdXNlcnMgdG8gYXZvaWQgdGhpcyBraW5kIG9mIGFjY2lkZW50IGFsbCB0 aGUgdGltZSBvZgo+IDJuZCBrZXJuZWwuCgpZZXMgeWVzLCBJIHVuZGVyc3RhbmQuIEJ1dCBpZiB0 aGUgY3Jhc2gga2VybmVsIGFsc28gZ2V0cyBzdHVjayB0aGV5IGhhdmUKbm8gbWVhbnMgb2YgcmVj b3ZlcnksIHJpZ2h0PyAob3RoZXIgdGhhbiBwb3dlciBjeWNsaW5nIHRoZSBoYXJkd2FyZSkKCkp1 c3QgcGxheWluZyBkZXZpbHMgYWR2b2NhdGUgaGVyZSwgSSBkb24ndCBhY3R1YWxseSBvYmplY3Qg dG8gdGhlIHBhdGNoLgoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX18Ka2V4ZWMgbWFpbGluZyBsaXN0CmtleGVjQGxpc3RzLmluZnJhZGVhZC5vcmcKaHR0cDov L2xpc3RzLmluZnJhZGVhZC5vcmcvbWFpbG1hbi9saXN0aW5mby9rZXhlYwo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752758AbbJAG1x (ORCPT ); Thu, 1 Oct 2015 02:27:53 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:58310 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750767AbbJAG1w (ORCPT ); Thu, 1 Oct 2015 02:27:52 -0400 Date: Thu, 1 Oct 2015 08:27:33 +0200 From: Peter Zijlstra To: =?utf-8?B?5rKz5ZCI6Iux5a6PIC8gS0FXQUnvvIxISURFSElSTw==?= Cc: Jonathan Corbet , Ingo Molnar , "Eric W. Biederman" , "H. Peter Anvin" , Andrew Morton , Thomas Gleixner , Vivek Goyal , "linux-doc@vger.kernel.org" , "x86@kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Michal Hocko , Ingo Molnar , =?utf-8?B?5bmz5p2+6ZuF5bezIC8gSElSQU1BVFXvvIxNQVNBTUk=?= Subject: Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Message-ID: <20151001062733.GL2881@worktop.programming.kicks-ass.net> References: <20150925112803.4258.94241.stgit@softrs> <20150925112811.4258.54494.stgit@softrs> <20150930115548.GI2881@worktop.programming.kicks-ass.net> <04EAB7311EE43145B2D3536183D1A8445499CD11@GSjpTKYDCembx31.service.hitachi.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <04EAB7311EE43145B2D3536183D1A8445499CD11@GSjpTKYDCembx31.service.hitachi.net> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 01, 2015 at 02:33:18AM +0000, 河合英宏 / KAWAI，HIDEHIRO wrote: > > On Fri, Sep 25, 2015 at 08:28:11PM +0900, Hidehiro Kawai wrote: > > > This patch introduces new boot option "noextnmi" which disables > > > external NMI. This option is useful for the dump capture kernel > > > so that an HA application or administrator wouldn't mistakenly > > > shoot down the kernel by NMI. > > > > So that they can get really stuck when the crash kernel crashes, right? > > ;-) > > No, it is different from my intention. > > `mistakenly' in the above means; they issue NMI due to a misconception > that the monitored host is stuck in the 1st kernel while it is actually > taking a crash dump in the 2nd kernel. To avoid this kind of accident, > there is a tool such as fence_kdump which notifies "I'm taking a crash > dump, so don't send NMI" to the HA clustering software. However, there > is a time window between kernel panic and the notification. > > "noextnmi" allows users to avoid this kind of accident all the time of > 2nd kernel. Yes yes, I understand. But if the crash kernel also gets stuck they have no means of recovery, right? (other than power cycling the hardware) Just playing devils advocate here, I don't actually object to the patch.