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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id y8sm18017619wma.10.2020.02.24.07.14.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2020 07:14:57 -0800 (PST) From: Vitaly Kuznetsov To: Sean Christopherson Cc: Paolo Bonzini , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 30/61] KVM: x86: Handle MPX CPUID adjustment in VMX code In-Reply-To: <20200201185218.24473-31-sean.j.christopherson@intel.com> References: <20200201185218.24473-1-sean.j.christopherson@intel.com> <20200201185218.24473-31-sean.j.christopherson@intel.com> Date: Mon, 24 Feb 2020 16:14:56 +0100 Message-ID: <874kvgow3z.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Sean Christopherson writes: > Move the MPX CPUID adjustments into VMX to eliminate an instance of the > undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the > common CPUID handling code. > > Note, VMX must manually check for kernel support via > boot_cpu_has(X86_FEATURE_MPX). > > No functional change intended. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/cpuid.c | 3 +-- > arch/x86/kvm/vmx/vmx.c | 14 ++++++++++++-- > 2 files changed, 13 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index cb5870a323cc..09e24d1d731c 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -340,7 +340,6 @@ static int __do_cpuid_func_emulated(struct kvm_cpuid_array *array, u32 func) > static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry) > { > unsigned f_invpcid = kvm_x86_ops->invpcid_supported() ? F(INVPCID) : 0; > - unsigned f_mpx = kvm_mpx_supported() ? F(MPX) : 0; > unsigned f_umip = kvm_x86_ops->umip_emulated() ? F(UMIP) : 0; > unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0; > unsigned f_la57; > @@ -349,7 +348,7 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry) > /* cpuid 7.0.ebx */ > const u32 kvm_cpuid_7_0_ebx_x86_features = > F(FSGSBASE) | F(BMI1) | F(HLE) | F(AVX2) | F(SMEP) | > - F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | f_mpx | F(RDSEED) | > + F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | 0 /*MPX*/ | F(RDSEED) | > F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) | > F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) | > F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt; > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 3ff830e2258e..143193fc178e 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -7106,8 +7106,18 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu) > > static void vmx_set_supported_cpuid(struct kvm_cpuid_entry2 *entry) > { > - if (entry->function == 1 && nested) > - entry->ecx |= feature_bit(VMX); > + switch (entry->function) { > + case 0x1: > + if (nested) > + cpuid_entry_set(entry, X86_FEATURE_VMX); > + break; > + case 0x7: > + if (boot_cpu_has(X86_FEATURE_MPX) && kvm_mpx_supported()) > + cpuid_entry_set(entry, X86_FEATURE_MPX); > + break; > + default: > + break; > + } > } > > static void vmx_request_immediate_exit(struct kvm_vcpu *vcpu) The word 'must' in the description seems to work like a trigger for reviewers, their brains automatically turn into 'and what if not?' mode :-) So do I understand correctly that kvm_mpx_supported() (which checks for XFEATURE_MASK_BNDREGS/XFEATURE_MASK_BNDCSR) may actually return true while 'boot_cpu_has(X86_FEATURE_MPX)' is false? Is this done on purpose, i.e. why don't we filter these out from vmcs_config early, similar to SVM? The patch itself looks good, so Reviewed-by: Vitaly Kuznetsov -- Vitaly