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=-8.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 55B10C433F5 for ; Fri, 3 Sep 2021 15:11:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 38CCA60EC0 for ; Fri, 3 Sep 2021 15:11:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239472AbhICPMw (ORCPT ); Fri, 3 Sep 2021 11:12:52 -0400 Received: from mga18.intel.com ([134.134.136.126]:53645 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229789AbhICPMv (ORCPT ); Fri, 3 Sep 2021 11:12:51 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10096"; a="206564378" X-IronPort-AV: E=Sophos;i="5.85,265,1624345200"; d="scan'208";a="206564378" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Sep 2021 08:11:51 -0700 X-IronPort-AV: E=Sophos;i="5.85,265,1624345200"; d="scan'208";a="534175292" Received: from achiranj-mobl.gar.corp.intel.com ([10.213.105.90]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Sep 2021 08:11:48 -0700 Message-ID: <3dd730013f98dde18b5a92ff56446703788195f9.camel@linux.intel.com> Subject: Re: Bug: d0e936adbd22 crashes at boot From: Srinivas Pandruvada To: Jens Axboe , LKML , "Rafael J. Wysocki" , Len Brown , inux-pm@vger.kernel.org Date: Fri, 03 Sep 2021 08:11:44 -0700 In-Reply-To: <767fe00f-bf31-1eb0-09cc-1be91c633bb4@kernel.dk> References: <942f4041-e4e7-1b08-3301-008ab37ff5b8@kernel.dk> <3ac87893-55ba-f2d4-bb1e-382868f12d4c@kernel.dk> <7f115f0476618d34b24ddec772acbbd7c0c4a572.camel@linux.intel.com> <767fe00f-bf31-1eb0-09cc-1be91c633bb4@kernel.dk> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.40.0-1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2021-09-03 at 09:00 -0600, Jens Axboe wrote: > On 9/3/21 8:38 AM, Srinivas Pandruvada wrote: > > On Fri, 2021-09-03 at 08:15 -0600, Jens Axboe wrote: > > > On 9/3/21 8:13 AM, Srinivas Pandruvada wrote: > > > > Hi Axboe, > > > > > > > > Thanks for reporting. > > > > On Fri, 2021-09-03 at 07:36 -0600, Jens Axboe wrote: > > > > > Hi, > > > > > > > > > > Booting Linus's tree causes a crash on my laptop, an x1 gen9. > > > > > This > > > > > was > > > > > a bit > > > > > difficult to pin down as it crashes before the display is up, > > > > > but I > > > > > managed > > > > > to narrow it down to: > > > > > > > > > > commit d0e936adbd2250cb03f2e840c6651d18edc22ace > > > > > Author: Srinivas Pandruvada < > > > > > srinivas.pandruvada@linux.intel.com> > > > > > Date:   Thu Aug 19 19:40:06 2021 -0700 > > > > > > > > > >     cpufreq: intel_pstate: Process HWP Guaranteed change > > > > > notification > > > > > > > > > > which crashes with a NULL pointer deref in > > > > > notify_hwp_interrupt() - > > > > > > > > > > > queue_delayed_work_on(). > > > > > > > > > > Reverting this change makes the laptop boot fine again. > > > > > > > > > Does this change fixes your issue? > > > > > > I would assume so, as it's crashing on cpudata == NULL :-) > > > > > > But why is it NULL? Happy to test patches, but the below doesn't > > > look > > > like > > > a real fix and more of a work-around. > > > > This platform is sending an HWP interrupt on a CPU which we didn't > > yet > > bring it up for pstate control. So somehow firmware decided to send > > very early during boot, which previously we would have ignored it > > > > Actually try this, with more prevention > > I can give this a whirl. > > > diff --git a/drivers/cpufreq/intel_pstate.c > > b/drivers/cpufreq/intel_pstate.c > > index b4ffe6c8a0d0..6ee88d7640ea 100644 > > --- a/drivers/cpufreq/intel_pstate.c > > +++ b/drivers/cpufreq/intel_pstate.c > > @@ -1645,12 +1645,24 @@ void notify_hwp_interrupt(void) > >         if (!hwp_active || !boot_cpu_has(X86_FEATURE_HWP_NOTIFY)) > >                 return; > >   > > -       rdmsrl(MSR_HWP_STATUS, value); > > +       rdmsrl_safe(MSR_HWP_STATUS, &value); > >         if (!(value & 0x01)) > >                 return; > >   > > +       /* > > +        * After hwp_active is set and all_cpu_data is allocated, > > there > > +        * is small window. > > +        */ > > +       if (!all_cpu_data) { > > +               wrmsrl_safe(MSR_HWP_STATUS, 0); > > +               return; > > +       } > > What synchronizes the all_cpu_data setup and the interrupt? Can the > interrupt come in while it's still being setup? Yes. I am working on a change to simulate that case and fix. Thanks, Srinivas >