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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 CD62DC4BA29 for ; Wed, 26 Feb 2020 20:41:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ABCA924656 for ; Wed, 26 Feb 2020 20:41:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727489AbgBZUlN (ORCPT ); Wed, 26 Feb 2020 15:41:13 -0500 Received: from mga06.intel.com ([134.134.136.31]:5071 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727350AbgBZUlN (ORCPT ); Wed, 26 Feb 2020 15:41:13 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Feb 2020 12:41:11 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,489,1574150400"; d="scan'208";a="350475837" Received: from jekeller-mobl1.amr.corp.intel.com (HELO [134.134.177.84]) ([134.134.177.84]) by fmsmga001.fm.intel.com with ESMTP; 26 Feb 2020 12:41:10 -0800 Subject: Re: [PATCH v5 13/19] x86/cpufeatures: Add flag to track whether MSR IA32_FEAT_CTL is configured From: Jacob Keller To: Sean Christopherson Cc: TonyWWang-oc@zhaoxin.com, acme@kernel.org, alexander.shishkin@linux.intel.com, bp@alien8.de, bp@suse.de, hpa@zytor.com, jacob.jun.pan@linux.intel.com, jarkko.sakkinen@linux.intel.com, jmattson@google.com, jolsa@redhat.com, joro@8bytes.org, kvm@vger.kernel.org, lenb@kernel.org, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-pm@vger.kernel.org, mark.rutland@arm.com, mingo@redhat.com, namhyung@kernel.org, pbonzini@redhat.com, peterz@infradead.org, rkrcmar@redhat.com, shuah@kernel.org, tglx@linutronix.de, tony.luck@intel.com, vkuznets@redhat.com, wanpengli@tencent.com, x86@kernel.org References: <20191221044513.21680-14-sean.j.christopherson@intel.com> <20200225221234.GL9245@linux.intel.com> <1eaf6fbe-0adb-5074-3bc4-1e8327e0cdb3@intel.com> <20200225232900.GO9245@linux.intel.com> <5434303a-0742-3811-fd14-6445d296c0f0@intel.com> <20200226004258.GP9245@linux.intel.com> Organization: Intel Corporation Message-ID: Date: Wed, 26 Feb 2020 12:41:09 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-edac-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org On 2/25/2020 4:58 PM, Jacob Keller wrote: > On 2/25/2020 4:42 PM, Sean Christopherson wrote>> So there's something > weird going on. Maybe "boot_cpu_has" in the >>> vmx_disabled_by_bios is wrong? Hmm. >> >> Hmm, perhaps a bug somewhere else is overwriting the cpufeatures bit for >> X86_FEATURE_VMX. Let me see if I can reproduce from net-next. >> > > If you have any further suggestions for debugging, I'm happy to help try > to figure this out. To my eyes, it looks like somehow bits get reset... > It's definitely not clear to me how this happens. > > There is the get_cpu_caps call.. but that seems to correctly call > apply_forced_caps at the end. > > That's all I have time for today. > > Thanks, > Jake > Hi, I kept digging into this, and I added a further print to the get_cpu_cap function. It looks like get_cpu_cap is being called again *after* init_ia32_feat_ctl... Digging further, I discovered this appears to be the call in setup_pku, which would only be enabled for systems which have X86_FEATURE_PKU enabled and supported. It's quite likely that test systems may not have had this feature, hence why it went undetected till now. Because of the extra get_cpu_cap call, the capabilities are reset. Since we never use setup_clear_cpu_cap or pass NULL to clear_cpu_cap, the code that sets the global cpu_caps_cleared bits is not run. It's not clear to me what the best fix for this is. Perhaps init_ia32_feat_ctl should be something run during early_identify_cpu, since it's really checking global status (rdmsr), and not per-CPU status. And then it could directly operate to call setup_clear_cpu_cap, which would properly clear the bit globally, ensuring that apply_forced_caps kicks in? Or this needs to somehow be run *after* setup_pku? But that doesn't feel very robust. Thanks, Jake