From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754040AbcFPL35 (ORCPT ); Thu, 16 Jun 2016 07:29:57 -0400 Received: from mga14.intel.com ([192.55.52.115]:64516 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751490AbcFPL3z (ORCPT ); Thu, 16 Jun 2016 07:29:55 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,480,1459839600"; d="scan'208";a="976952426" Date: Thu, 16 Jun 2016 19:29:51 +0800 From: Haozhong Zhang To: Paolo Bonzini Cc: kvm@vger.kernel.org, rkrcmar@redhat.com, Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Gleb Natapov , Boris Petkov , Tony Luck , Andi Kleen , Ashok Raj Subject: Re: [PATCH v2 2/3] KVM: VMX: validate individual bits of guest MSR_IA32_FEATURE_CONTROL Message-ID: <20160616112951.vt67sjbktozltb5t@hz-desktop> Mail-Followup-To: Paolo Bonzini , kvm@vger.kernel.org, rkrcmar@redhat.com, Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Gleb Natapov , Boris Petkov , Tony Luck , Andi Kleen , Ashok Raj References: <20160616060531.30028-1-haozhong.zhang@intel.com> <20160616060531.30028-3-haozhong.zhang@intel.com> <088f9fcb-a648-05d4-530a-790cb084bd09@redhat.com> <20160616111655.ltcgle2cju2fksrx@hz-desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.1-neo (2016-05-02) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/16/16 13:19, Paolo Bonzini wrote: > > > On 16/06/2016 13:16, Haozhong Zhang wrote: > >> However, I think FEATURE_CONTROL_LOCKED should always be writable. If > >> you change that, it's simpler to just do |= and &= in the caller. > > > > These two functions (add/del) are to prevent callers from forgetting > > setting/clearing FEATURE_CONTROL_LOCKED in > > msr_ia32_feature_control_valid_bits: it should be set if any feature > > bit is set, and be cleared if all feature bits are cleared. The second > > rule could relaxed as we can always present MSR_IA32_FEATURE_CONTROL > > to guest. > > Yes, this means that FEATURE_CONTROL_LOCKED effectively is always valid. > So you end up with just &= to clear and |= to set. > > > I'm okey to let callers take care for the locked bit. > > > >>> + to_vmx(vcpu)->msr_ia32_feature_control_valid_bits |= > >>> + bits | FEATURE_CONTROL_LOCKED; > >>> +} > >>> + > >>> +static void feature_control_valid_bits_del(struct kvm_vcpu *vcpu, uint64_t bits) > >>> +{ > >>> + uint64_t *valid_bits = > >>> + &to_vmx(vcpu)->msr_ia32_feature_control_valid_bits; > >>> + ASSERT(!(bits & ~FEATURE_CONTROL_MAX_VALID_BITS)); > >>> + *valid_bits &= ~bits; > >>> + if (!(*valid_bits & ~FEATURE_CONTROL_LOCKED)) > >>> + *valid_bits = 0; > >>> +} > >>> + > >>> #define VMCS12_OFFSET(x) offsetof(struct vmcs12, x) > >>> #define FIELD(number, name) [number] = VMCS12_OFFSET(name) > >>> #define FIELD64(number, name) [number] = VMCS12_OFFSET(name), \ > >>> @@ -2864,6 +2897,14 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata) > >>> return 0; > >>> } > >>> > >>> +static inline bool vmx_feature_control_msr_valid(struct kvm_vcpu *vcpu, > >>> + uint64_t val) > >>> +{ > >>> + uint64_t valid_bits = to_vmx(vcpu)->msr_ia32_feature_control_valid_bits; > >>> + > >>> + return valid_bits && !(val & ~valid_bits); > >>> +} > >>> /* > >>> * Reads an msr value (of 'msr_index') into 'pdata'. > >>> * Returns 0 on success, non-0 otherwise. > >>> @@ -2906,7 +2947,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > >>> msr_info->data = vmcs_read64(GUEST_BNDCFGS); > >>> break; > >>> case MSR_IA32_FEATURE_CONTROL: > >>> - if (!nested_vmx_allowed(vcpu)) > >>> + if (!vmx_feature_control_msr_valid(vcpu, 0)) > >> > >> You can remove this if completely in patch 1. It's okay to make the MSR > >> always available. > >> > > > > But then it also allows all bits to be set by guests, even though some > > features are not available. > > Note that this is "get". Of course the "if" must stay in vmx_set_msr. > My mistake. I'll remove it in patch 1. Thanks, Haozhong