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=-2.2 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 87A74C43603 for ; Wed, 11 Dec 2019 16:35:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 595952073D for ; Wed, 11 Dec 2019 16:35:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730710AbfLKQfM (ORCPT ); Wed, 11 Dec 2019 11:35:12 -0500 Received: from mga06.intel.com ([134.134.136.31]:1794 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730447AbfLKQfM (ORCPT ); Wed, 11 Dec 2019 11:35:12 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Dec 2019 08:35:10 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,301,1571727600"; d="scan'208";a="245344346" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by fmsmga002.fm.intel.com with ESMTP; 11 Dec 2019 08:35:10 -0800 Date: Wed, 11 Dec 2019 08:35:10 -0800 From: Sean Christopherson To: Yang Weijiang Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com, yu.c.zhang@linux.intel.com, yu-cheng.yu@intel.com Subject: Re: [PATCH v8 4/7] KVM: VMX: Load CET states on vmentry/vmexit Message-ID: <20191211163510.GF5044@linux.intel.com> References: <20191101085222.27997-1-weijiang.yang@intel.com> <20191101085222.27997-5-weijiang.yang@intel.com> <20191210212305.GM15758@linux.intel.com> <20191211015423.GC12845@local-michael-cet-test> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191211015423.GC12845@local-michael-cet-test> 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 Wed, Dec 11, 2019 at 09:54:23AM +0800, Yang Weijiang wrote: > On Tue, Dec 10, 2019 at 01:23:05PM -0800, Sean Christopherson wrote: > > On Fri, Nov 01, 2019 at 04:52:19PM +0800, Yang Weijiang wrote: > > > @@ -2834,6 +2837,9 @@ void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) > > > struct vcpu_vmx *vmx = to_vmx(vcpu); > > > unsigned long hw_cr0; > > > > > > + if (!(cr0 & X86_CR0_WP) && kvm_read_cr4_bits(vcpu, X86_CR4_CET)) > > > + cr0 |= X86_CR0_WP; > > > > Huh? What's the interaction between CR4.CET and CR0.WP? If there really > > is some non-standard interaction then it needs to be documented in at least > > the changelog and probably with a comment as well. > > > The processor does not allow CR4.CET to be set if CR0.WP = 0 (similarly, it > does not allow CR0.WP to be cleared while CR4.CET = 1). Ya, as you surmised below, this needs to be a #GP condition. Have you tested SMM at all? The interaction between CR0 and CR4 may be problematic for em_rsm() and/or rsm_enter_protected_mode(). > > > + > > > hw_cr0 = (cr0 & ~KVM_VM_CR0_ALWAYS_OFF); > > > if (enable_unrestricted_guest) > > > hw_cr0 |= KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST; > > > @@ -2936,6 +2942,22 @@ static bool guest_cet_allowed(struct kvm_vcpu *vcpu, u32 feature, u32 mode) > > > return false; > > > } > > > > > > +bool is_cet_bit_allowed(struct kvm_vcpu *vcpu) > > > +{ > > > + unsigned long cr0; > > > + bool cet_allowed; > > > + > > > + cr0 = kvm_read_cr0(vcpu); > > > + cet_allowed = guest_cet_allowed(vcpu, X86_FEATURE_SHSTK, > > > + XFEATURE_MASK_CET_USER) || > > > + guest_cet_allowed(vcpu, X86_FEATURE_IBT, > > > + XFEATURE_MASK_CET_USER); > > > + if ((cr0 & X86_CR0_WP) && cet_allowed) > > > + return true; > > > > So, attempting to set CR4.CET if CR0.WP=0 takes a #GP? But attempting > > to clear CR0.WP if CR4.CET=1 is ignored? > > > Per above words in spec., inject #GP to guest in either case? > > > > + > > > + return false; > > > +} > > > +