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 <[email protected]> Signed-off-by: Zhang Yi Z <[email protected]> Signed-off-by: Yang Weijiang <[email protected]> --- 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 13745f2a5ecd..a9f135c52cbc 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3126,6 +3126,13 @@ void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long pgd) 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); @@ -7230,6 +7237,42 @@ 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); @@ -7268,6 +7311,9 @@ 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 88c593f83b28..ea8a9dc9fbad 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -184,6 +184,9 @@ 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) + u64 __read_mostly host_efer; EXPORT_SYMBOL_GPL(host_efer); -- 2.17.2
