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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.googlemail.com with ESMTPSA id pw28sm2623456ejb.115.2021.01.28.10.04.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 Jan 2021 10:04:07 -0800 (PST) Sender: Paolo Bonzini Subject: Re: [PATCH v14 11/13] KVM: VMX: Pass through CET MSRs to the guest when supported From: Paolo Bonzini To: Yang Weijiang , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com, jmattson@google.com Cc: yu.c.zhang@linux.intel.com References: <20201106011637.14289-1-weijiang.yang@intel.com> <20201106011637.14289-12-weijiang.yang@intel.com> <78948a28-2b6c-fccb-971a-550ea7e4da2c@redhat.com> Message-ID: Date: Thu, 28 Jan 2021 19:04:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <78948a28-2b6c-fccb-971a-550ea7e4da2c@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/01/21 18:54, Paolo Bonzini wrote: > On 06/11/20 02:16, Yang Weijiang wrote: >> Pass through all CET MSRs when the associated CET component (kernel vs. >> user) is enabled to improve guest performance.  All CET MSRs are context >> switched, either via dedicated VMCS fields or XSAVES. >> >> Co-developed-by: Zhang Yi Z >> Signed-off-by: Zhang Yi Z >> Co-developed-by: Sean Christopherson >> Signed-off-by: Sean Christopherson >> Signed-off-by: Yang Weijiang >> --- >>   arch/x86/kvm/vmx/vmx.c | 29 +++++++++++++++++++++++++++++ >>   1 file changed, 29 insertions(+) >> >> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >> index c88a6e1721b1..6ba2027a3d44 100644 >> --- a/arch/x86/kvm/vmx/vmx.c >> +++ b/arch/x86/kvm/vmx/vmx.c >> @@ -7366,6 +7366,32 @@ static void update_intel_pt_cfg(struct kvm_vcpu >> *vcpu) >>           vmx->pt_desc.ctl_bitmask &= ~(0xfULL << (32 + i * 4)); >>   } >> +static bool is_cet_state_supported(struct kvm_vcpu *vcpu, u32 xss_state) >> +{ >> +    return (vcpu->arch.guest_supported_xss & xss_state) && >> +           (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) || >> +        guest_cpuid_has(vcpu, X86_FEATURE_IBT)); >> +} >> + >> +static void vmx_update_intercept_for_cet_msr(struct kvm_vcpu *vcpu) >> +{ >> +    bool incpt = !is_cet_state_supported(vcpu, XFEATURE_MASK_CET_USER); >> + >> +    vmx_set_intercept_for_msr(vcpu, MSR_IA32_U_CET, MSR_TYPE_RW, incpt); >> + >> +    incpt |= !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK); >> +    vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL3_SSP, MSR_TYPE_RW, >> incpt); >> + >> +    incpt = !is_cet_state_supported(vcpu, XFEATURE_MASK_CET_KERNEL); >> +    vmx_set_intercept_for_msr(vcpu, MSR_IA32_S_CET, MSR_TYPE_RW, incpt); >> + >> +    incpt |= !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK); >> +    vmx_set_intercept_for_msr(vcpu, MSR_IA32_INT_SSP_TAB, >> MSR_TYPE_RW, incpt); >> +    vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL0_SSP, MSR_TYPE_RW, >> incpt); >> +    vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL1_SSP, MSR_TYPE_RW, >> incpt); >> +    vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL2_SSP, MSR_TYPE_RW, >> incpt); >> +} >> + >>   static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) >>   { >>       struct vcpu_vmx *vmx = to_vmx(vcpu); >> @@ -7409,6 +7435,9 @@ static void vmx_vcpu_after_set_cpuid(struct >> kvm_vcpu *vcpu) >>       /* Refresh #PF interception to account for MAXPHYADDR changes. */ >>       update_exception_bitmap(vcpu); >> + >> +    if (kvm_cet_supported()) >> +        vmx_update_intercept_for_cet_msr(vcpu); >>   } >>   static __init void vmx_set_cpu_caps(void) >> > > Can you do this only if CR4.CET=1? Actually, considering this is XSAVES and not RDMSR/WRMSR state, this is okay as is. Paolo