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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 B9362C31E4B for ; Fri, 14 Jun 2019 14:14:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97F6721537 for ; Fri, 14 Jun 2019 14:14:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728752AbfFNOOZ (ORCPT ); Fri, 14 Jun 2019 10:14:25 -0400 Received: from mga09.intel.com ([134.134.136.24]:13630 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727698AbfFNOOZ (ORCPT ); Fri, 14 Jun 2019 10:14:25 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Jun 2019 07:14:24 -0700 X-ExtLoop1: 1 Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.36]) by orsmga007.jf.intel.com with ESMTP; 14 Jun 2019 07:14:24 -0700 Date: Fri, 14 Jun 2019 07:14:24 -0700 From: Sean Christopherson To: Borislav Petkov Cc: Fenghua Yu , Thomas Gleixner , Ingo Molnar , H Peter Anvin , Ravi V Shankar , linux-kernel , x86 , Radim =?utf-8?B?S3LEjW3DocWZ?= , Paolo Bonzini Subject: Re: [RFC PATCH 2/3] x86/cpufeatures: Combine word 11 and 12 into new scattered features word 11 Message-ID: <20190614141424.GA12191@linux.intel.com> References: <1560459064-195037-1-git-send-email-fenghua.yu@intel.com> <1560459064-195037-3-git-send-email-fenghua.yu@intel.com> <20190614114410.GD2586@zn.tnic> <20190614122749.GE2586@zn.tnic> <20190614131701.GA198207@romley-ivt3.sc.intel.com> <20190614134123.GF2586@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190614134123.GF2586@zn.tnic> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 14, 2019 at 03:41:23PM +0200, Borislav Petkov wrote: > + Radim and Paolo. See upthread for context. > > On Fri, Jun 14, 2019 at 06:17:02AM -0700, Fenghua Yu wrote: > > > Alternatively - and what I think is the better solution - would be to > > > remove those BUILD_BUG_ONs in x86_feature_cpuid and filter out the > > > Linux-defined leafs dynamically. This way the array won't have holes in > > > it. > > > > Maybe adding a dummy slot in cpuid_leafs in patch 0002 to avoid the > > compilation errors? > > Maybe you didn't read what you're replying to: "This way the array > won't have holes in it". Ontop of yours: > > diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h > index d78a61408243..03d6f3f7b27c 100644 > --- a/arch/x86/kvm/cpuid.h > +++ b/arch/x86/kvm/cpuid.h > @@ -47,6 +47,7 @@ static const struct cpuid_reg reverse_cpuid[] = { > [CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX}, > [CPUID_7_0_EBX] = { 7, 0, CPUID_EBX}, > [CPUID_D_1_EAX] = { 0xd, 1, CPUID_EAX}, > + [CPUID_7_1_EAX] = { 7, 1, CPUID_EAX}, > [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX}, > [CPUID_6_EAX] = { 6, 0, CPUID_EAX}, > [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX}, > @@ -59,8 +60,9 @@ static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned x86_feature) > { > unsigned x86_leaf = x86_feature / 32; > > - BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid)); > - BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0); > + if (x86_leaf == CPUID_LNX_1 || > + x86_leaf == CPUID_LNX_4) > + return NULL; > > return reverse_cpuid[x86_leaf]; > } > > That's what I mean with filter out dynamically. This is wrong. KVM isn't complaining about shuffling the order of feature words, it's complaining that code is trying to do a reverse CPUID lookup to a feature that isn't in the reverse_cpuid table. Filtering out checks dynamically is just hiding bugs. >In function ‘x86_feature_cpuid’, > inlined from ‘guest_cpuid_get_register’ at arch/x86/kvm/cpuid.h:71:33, > inlined from ‘guest_cpuid_has’ at arch/x86/kvm/cpuid.h:100:8, > inlined from ‘kvm_get_msr_common’ at arch/x86/kvm/x86.c:2804:8: This corresponds to "guest_cpuid_has(vcpu, X86_FEATURE_ARCH_CAPABILITIES)", i.e. KVM is trying to query X86_FEATURE_ARCH_CAPABILITIES and is yelling that there is no reverse_cpuid entry for CPUID_7_EDX. The problem is that 'enum cpuid_leafs' no longer matches up with the word numbers defined in cpufeatures.h, e.g. CPUID_7_EDX == 17 or so, but the entries in cpufeatures.h defined CPUID_7_EDX flags using word 18. This patch also needs to modify NCAPINTS.