From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752182AbbIBDup (ORCPT ); Tue, 1 Sep 2015 23:50:45 -0400 Received: from ud10.udmedia.de ([194.117.254.50]:40590 "EHLO mail.ud10.udmedia.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751124AbbIBDun (ORCPT ); Tue, 1 Sep 2015 23:50:43 -0400 Date: Wed, 2 Sep 2015 05:50:40 +0200 From: Markus Trippelsdorf To: Xiao Guangrong Cc: Ingo Molnar , Linus Torvalds , linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner , Andrew Morton , Mike Galbraith , Joerg Roedel , Paolo Bonzini , kvm@vger.kernel.org Subject: Re: commit 3c2e7f7de3 (KVM use NPT page attributes) causes boot failures Message-ID: <20150902035040.GA420@x4> References: <20150901070856.GA430@x4> <20150901072741.GB20383@gmail.com> <20150901074449.GB430@x4> <20150901083856.GD25398@gmail.com> <20150901084444.GB421@x4> <20150901085627.GF6315@gmail.com> <20150901100417.GA424@x4> <55E5A157.5040403@linux.intel.com> <20150901135636.GA423@x4> <55E6273D.6080701@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55E6273D.6080701@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2015.09.02 at 06:31 +0800, Xiao Guangrong wrote: > > > On 09/01/2015 09:56 PM, Markus Trippelsdorf wrote: > > On 2015.09.01 at 21:00 +0800, Xiao Guangrong wrote: > >> > >> Did it trigger the BUG()/BUG_ON() in mtrr2protval()/fallback_mtrr_type()? > >> If yes, could you please print the actual value out? > > > > It is the BUG() in fallback_mtrr_type(). I changed it to a printk and > > it prints 1 for the value of mtrr. > > > > MTRR_TYPE_WRCOMB 1 > > > > Then I suspect pat is not enabled in your box, could you please check > CONFIG_X86_PAT is selected in your .config file, pat is shown in > /proc/cpuid, "nopat" kernel parameter is used, and dmesg | grep PAT. No. PAT is of course enabled and booting is successful sometimes even with the BUG() in allback_mtrr_type(). I suspect a setup (timing) issue. markus@x4 linux % cat .config | grep X86_PAT CONFIG_X86_PAT=y markus@x4 linux % dmesg | grep PAT [ 0.000000] x86/PAT: Configuration [0-7]: WB WC UC- UC WB WC UC- WT markus@x4 linux % cat /proc/cpuinfo| grep pat flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt hw_pstate npt lbrv svm_lock nrip_save vmmcall ... -- Markus