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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 9521CC10F27 for ; Tue, 10 Mar 2020 17:10:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 76D6A21D56 for ; Tue, 10 Mar 2020 17:10:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726616AbgCJRKS (ORCPT ); Tue, 10 Mar 2020 13:10:18 -0400 Received: from mga14.intel.com ([192.55.52.115]:37450 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726295AbgCJRKS (ORCPT ); Tue, 10 Mar 2020 13:10:18 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Mar 2020 10:10:17 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,537,1574150400"; d="scan'208";a="443241331" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by fmsmga006.fm.intel.com with ESMTP; 10 Mar 2020 10:10:17 -0700 Date: Tue, 10 Mar 2020 10:10:17 -0700 From: Sean Christopherson To: Paolo Bonzini Cc: Jim Mattson , Vitaly Kuznetsov , Wanpeng Li , Joerg Roedel , kvm list , LKML , Pu Wen Subject: Re: [PATCH v2 4/7] KVM: x86: Fix CPUID range checks for Hypervisor and Centaur classes Message-ID: <20200310171017.GC9305@linux.intel.com> References: <20200305013437.8578-1-sean.j.christopherson@intel.com> <20200305013437.8578-5-sean.j.christopherson@intel.com> <20200305192532.GN11500@linux.intel.com> <20200305215149.GS11500@linux.intel.com> <5567edf6-a04c-5810-8ed5-78a0db14b202@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5567edf6-a04c-5810-8ed5-78a0db14b202@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Mar 06, 2020 at 10:03:37AM +0100, Paolo Bonzini wrote: > On 05/03/20 22:51, Sean Christopherson wrote: > >> Ah. So cross-vendor CPUID specifications are not supported? > > Cross-vendor CPUID is sort of allowed? E.g. this plays nice with creating > > a Centaur CPU on an Intel platform. My interpretation of GET_SUPPORTED... > > is that KVM won't prevent enumerating what you want in CPUID, but it only > > promises to correctly support select leafs. > > But in practice does this change anything? If the vendor is not Centaur > it's unlikely that there is a 0xc0000000 leaf. The 0x80000000 bound is > certainly not going to be at 0xc0000000 or beyond, and likewise to 0xc0000000 > bound is not going to be at 0xd0000000 or beyond. So I'm not sure if > anything is lost from this simplification: Probably not? But in the unlikely scenario that Intel wants to add a CPUID leaf above 0xc0000000, I don't want to have to explain that it might cause problems for KVM guests because I added code to emulate (alleged) Centaur behavior for virtual Intel CPUs. > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index ed5e0bda672c..f43a8875c126 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -963,8 +963,7 @@ static bool cpuid_function_in_range(struct kvm_vcpu *vcpu, u32 function) > > if (function >= 0x40000000 && function <= 0x4fffffff) > class = kvm_find_cpuid_entry(vcpu, function & 0xffffff00, 0); > - else if (function >= 0xc0000000 && function <= 0xcfffffff && > - is_guest_vendor_centaur(basic->ebx, basic->ecx, basic->edx)) > + else if (function >= 0xc0000000) > class = kvm_find_cpuid_entry(vcpu, 0xc0000000, 0); > else > class = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0); > diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h > index 12ddfa493bae..3cb50eda606d 100644 > --- a/arch/x86/kvm/kvm_emulate.h > +++ b/arch/x86/kvm/kvm_emulate.h > @@ -424,13 +424,6 @@ static inline bool is_guest_vendor_hygon(u32 ebx, u32 ecx, u32 edx) > edx == X86EMUL_CPUID_VENDOR_HygonGenuine_edx; > } > > -static inline bool is_guest_vendor_centaur(u32 ebx, u32 ecx, u32 edx) > -{ > - return ebx == X86EMUL_CPUID_VENDOR_CentaurHauls_ebx && > - ecx == X86EMUL_CPUID_VENDOR_CentaurHauls_ecx && > - edx == X86EMUL_CPUID_VENDOR_CentaurHauls_edx; > -} > - > enum x86_intercept_stage { > X86_ICTP_NONE = 0, /* Allow zero-init to not match anything */ > X86_ICPT_PRE_EXCEPT, >