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 BC4E9C43603 for ; Thu, 12 Dec 2019 01:03:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 86AC92077B for ; Thu, 12 Dec 2019 01:03:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727512AbfLLBDF (ORCPT ); Wed, 11 Dec 2019 20:03:05 -0500 Received: from mga05.intel.com ([192.55.52.43]:61888 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727403AbfLLBDF (ORCPT ); Wed, 11 Dec 2019 20:03:05 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Dec 2019 17:03:04 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,303,1571727600"; d="scan'208";a="210945278" Received: from local-michael-cet-test.sh.intel.com (HELO localhost) ([10.239.159.128]) by fmsmga008.fm.intel.com with ESMTP; 11 Dec 2019 17:03:03 -0800 Date: Thu, 12 Dec 2019 09:04:24 +0800 From: Yang Weijiang To: Sean Christopherson Cc: Yang Weijiang , 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: <20191212010423.GB17570@local-michael-cet-test.sh.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> <20191211163510.GF5044@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191211163510.GF5044@linux.intel.com> User-Agent: Mutt/1.11.3 (2019-02-01) 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 08:35:10AM -0800, Sean Christopherson wrote: > 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. > OK, will do it. > Have you tested SMM at all? The interaction between CR0 and CR4 may be > problematic for em_rsm() and/or rsm_enter_protected_mode(). > Not yet, what's an easy way to test code in SMM mode? Thanks! > > > > + > > > > 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; > > > > +} > > > > +