From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43385C55185 for ; Wed, 22 Apr 2020 11:01:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C25220774 for ; Wed, 22 Apr 2020 11:01:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732290AbgDVLBe (ORCPT ); Wed, 22 Apr 2020 07:01:34 -0400 Received: from mx2.suse.de ([195.135.220.15]:49028 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726579AbgDVLB1 (ORCPT ); Wed, 22 Apr 2020 07:01:27 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 30876ABD6; Wed, 22 Apr 2020 11:01:25 +0000 (UTC) Message-ID: <1587553284.9537.96.camel@suse.cz> Subject: Re: [BISECTED]: Kernel panic (was: Linux 5.7-rc2) From: Giovanni Gherdovich To: Harald Arnesen , Peter Zijlstra , Linus Torvalds , Dave Kleikamp Cc: Ingo Molnar , "Rafael J. Wysocki" , Linux Kernel Mailing List Date: Wed, 22 Apr 2020 13:01:24 +0200 In-Reply-To: References: <428bac87-b6dd-0867-c8f8-622cd606de3e@skogtun.org> <20200421212347.GV2483@worktop.programming.kicks-ass.net> <1587546150.9537.84.camel@suse.cz> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2020-04-22 at 12:22 +0200, Harald Arnesen wrote: > Harald Arnesen [22.04.2020 11:37]: > > > Giovanni Gherdovich [22.04.2020 11:02]: > > > > > > Harald: > > > > > > I'll echo Linus' request of testing that the patch series linked above fixes > > > the problem on your machine. Since you're testing -rc kernels and bisecting > > > bugs I assume you're comfortable with patching and compiling kernels, but if > > > that is not the case I am more than happy to assist by providing either an RPM > > > or a DEB package, depending on the distribution you're running. Let me know. > > Will try patching first, if I'm not successful, you may compile a DEB > > package for me. > > I can confirm that my Thinkpad T510i boots normally with the four > patches added. > > Thanks! That's awesome, thank you for testing. Regarding the turbostat output you attached to an earlier email, it confirms the suspicion that the 4C turbo is reported as zero (being a 2 cores / 4 threads machine), explaining why the fix works: cpu2: MSR_TURBO_RATIO_LIMIT: 0x00001313 19 * 133.3 = 2533.3 MHz max turbo 2 active cores 19 * 133.3 = 2533.3 MHz max turbo 1 active cores In the above, bits 31:24 are zero. It's not a universal rule, though: my laptop also has a 2 cores / 4 threads cpu, and that same MSR says: cpu3: MSR_TURBO_RATIO_LIMIT: 0x1b1b1b1b1b1d 27 * 100.0 = 2700.0 MHz max turbo 6 active cores 27 * 100.0 = 2700.0 MHz max turbo 5 active cores 27 * 100.0 = 2700.0 MHz max turbo 4 active cores 27 * 100.0 = 2700.0 MHz max turbo 3 active cores 27 * 100.0 = 2700.0 MHz max turbo 2 active cores 29 * 100.0 = 2900.0 MHz max turbo 1 active cores So despite my CPU being similar to yours, it wouldn't show the bug. There is even more: the bug can show on large core counts too, as seen in https://lore.kernel.org/lkml/bf43772d-48e5-01d4-dd03-330110e487fa@linux.intel.com/ Like Xu from Intel has an Atom P-Series with 24 physical cores, yet their MSR goes like: MSR_TURBO_RATIO_LIMIT: 0x00000016 which means only the 1C turbo is reported non-zero (that machine doesn't have turbo at all, 1C turbo is the same as base frequency). Thanks, Giovanni