Messages in this thread | | | Subject | Re: [PATCH v13 03/11] KVM: VMX: Set guest CET MSRs per KVM and host configuration | From | Xiaoyao Li <> | Date | Thu, 2 Jul 2020 23:13:35 +0800 |
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On 7/1/2020 4:04 PM, Yang Weijiang wrote: > CET MSRs pass through guest directly to enhance performance. CET runtime > control settings are stored in MSR_IA32_{U,S}_CET, Shadow Stack Pointer(SSP) > are stored in MSR_IA32_PL{0,1,2,3}_SSP, SSP table base address is stored in > MSR_IA32_INT_SSP_TAB, these MSRs are defined in kernel and re-used here. > > MSR_IA32_U_CET and MSR_IA32_PL3_SSP are used for user-mode protection,the MSR > contents are switched between threads during scheduling, it makes sense to pass > through them so that the guest kernel can use xsaves/xrstors to operate them > efficiently. Other MSRs are used for non-user mode protection. See SDM for detailed > info. > > The difference between CET VMCS fields and CET MSRs is that,the former are used > during VMEnter/VMExit, whereas the latter are used for CET state storage between > task/thread scheduling. > > Co-developed-by: Zhang Yi Z <yi.z.zhang@linux.intel.com> > Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com> > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com> > --- > arch/x86/kvm/vmx/vmx.c | 46 ++++++++++++++++++++++++++++++++++++++++++ > arch/x86/kvm/x86.c | 3 +++ > 2 files changed, 49 insertions(+) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index d52d470e36b1..97e766875a7e 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -3020,6 +3020,13 @@ void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long cr3) > vmcs_writel(GUEST_CR3, guest_cr3); > } > > +static bool is_cet_state_supported(struct kvm_vcpu *vcpu, u32 xss_states) > +{ > + return ((supported_xss & xss_states) && > + (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) || > + guest_cpuid_has(vcpu, X86_FEATURE_IBT))); > +} > + > int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > @@ -7098,6 +7105,42 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu) > vmx->pt_desc.ctl_bitmask &= ~(0xfULL << (32 + i * 4)); > } > > +static void vmx_update_intercept_for_cet_msr(struct kvm_vcpu *vcpu) > +{ > + struct vcpu_vmx *vmx = to_vmx(vcpu); > + unsigned long *msr_bitmap = vmx->vmcs01.msr_bitmap; > + bool incpt; > + > + incpt = !is_cet_state_supported(vcpu, XFEATURE_MASK_CET_USER); > + /* > + * U_CET is required for USER CET, and U_CET, PL3_SPP are bound as > + * one component and controlled by IA32_XSS[bit 11]. > + */ > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_U_CET, MSR_TYPE_RW, > + incpt); > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_PL3_SSP, MSR_TYPE_RW, > + incpt); > + > + incpt = !is_cet_state_supported(vcpu, XFEATURE_MASK_CET_KERNEL); > + /* > + * S_CET is required for KERNEL CET, and PL0_SSP ... PL2_SSP are > + * bound as one component and controlled by IA32_XSS[bit 12]. > + */ > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_S_CET, MSR_TYPE_RW, > + incpt); > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_PL0_SSP, MSR_TYPE_RW, > + incpt); > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_PL1_SSP, MSR_TYPE_RW, > + incpt); > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_PL2_SSP, MSR_TYPE_RW, > + incpt); > + > + incpt |= !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK); > + /* SSP_TAB is only available for KERNEL SHSTK.*/ > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW, > + incpt); > +} > + > static void vmx_cpuid_update(struct kvm_vcpu *vcpu) > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > @@ -7136,6 +7179,9 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu) > vmx_set_guest_msr(vmx, msr, enabled ? 0 : TSX_CTRL_RTM_DISABLE); > } > } > + > + if (supported_xss & (XFEATURE_MASK_CET_KERNEL | XFEATURE_MASK_CET_USER)) > + vmx_update_intercept_for_cet_msr(vcpu); > } > > static __init void vmx_set_cpu_caps(void) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index c5835f9cb9ad..6390b62c12ed 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -186,6 +186,9 @@ static struct kvm_shared_msrs __percpu *shared_msrs; > | XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \ > | XFEATURE_MASK_PKRU) > > +#define KVM_SUPPORTED_XSS (XFEATURE_MASK_CET_USER | \ > + XFEATURE_MASK_CET_KERNEL) > +
This definition need to be moved to Patch 5?
> u64 __read_mostly host_efer; > EXPORT_SYMBOL_GPL(host_efer); > >
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