diff options
| -rw-r--r-- | arch/x86/kvm/vmx/capabilities.h | 4 | ||||
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 15 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 12 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.h | 1 |
4 files changed, 32 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h index f614428dbeda..59c83888bdc0 100644 --- a/arch/x86/kvm/vmx/capabilities.h +++ b/arch/x86/kvm/vmx/capabilities.h @@ -100,6 +100,10 @@ static inline bool cpu_has_load_perf_global_ctrl(void) return vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL; } +static inline bool cpu_has_load_cet_ctrl(void) +{ + return (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_CET_STATE); +} static inline bool cpu_has_vmx_mpx(void) { return vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_BNDCFGS; diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index bde768c7111f..4ab066a3c22f 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4312,6 +4312,21 @@ void vmx_set_constant_host_state(struct vcpu_vmx *vmx) if (cpu_has_load_ia32_efer()) vmcs_write64(HOST_IA32_EFER, kvm_host.efer); + + /* + * Supervisor shadow stack is not enabled on host side, i.e., + * host IA32_S_CET.SHSTK_EN bit is guaranteed to 0 now, per SDM + * description(RDSSP instruction), SSP is not readable in CPL0, + * so resetting the two registers to 0s at VM-Exit does no harm + * to kernel execution. When execution flow exits to userspace, + * SSP is reloaded from IA32_PL3_SSP. Check SDM Vol.2A/B Chapter + * 3 and 4 for details. + */ + if (cpu_has_load_cet_ctrl()) { + vmcs_writel(HOST_S_CET, kvm_host.s_cet); + vmcs_writel(HOST_SSP, 0); + vmcs_writel(HOST_INTR_SSP_TABLE, 0); + } } void set_cr4_guest_host_mask(struct vcpu_vmx *vmx) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 54d280fe9a4b..0050509a7de2 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9997,6 +9997,18 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) return -EIO; } + if (boot_cpu_has(X86_FEATURE_SHSTK) || boot_cpu_has(X86_FEATURE_IBT)) { + rdmsrq(MSR_IA32_S_CET, kvm_host.s_cet); + /* + * Linux doesn't yet support supervisor shadow stacks (SSS), so + * KVM doesn't save/restore the associated MSRs, i.e. KVM may + * clobber the host values. Yell and refuse to load if SSS is + * unexpectedly enabled, e.g. to avoid crashing the host. + */ + if (WARN_ON_ONCE(kvm_host.s_cet & CET_SHSTK_EN)) + return -EIO; + } + memset(&kvm_caps, 0, sizeof(kvm_caps)); x86_emulator_cache = kvm_alloc_emulator_cache(); diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index 076eccba0f7e..65cbd454c4f1 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -50,6 +50,7 @@ struct kvm_host_values { u64 efer; u64 xcr0; u64 xss; + u64 s_cet; u64 arch_capabilities; }; |