Messages in this thread | | | Subject | Re: [PATCH v2] KVM: VMX: Enable Notify VM exit | From | Tao Xu <> | Date | Thu, 3 Jun 2021 09:23:58 +0800 |
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On 6/2/21 6:31 PM, Vitaly Kuznetsov wrote: > Tao Xu <tao3.xu@intel.com> writes: > >> There are some cases that malicious virtual machines can cause CPU stuck >> (event windows don't open up), e.g., infinite loop in microcode when >> nested #AC (CVE-2015-5307). No event window obviously means no events, >> e.g. NMIs, SMIs, and IRQs will all be blocked, may cause the related >> hardware CPU can't be used by host or other VM. >> >> To resolve those cases, it can enable a notify VM exit if no event >> window occur in VMX non-root mode for a specified amount of time >> (notify window). Since CPU is first observed the risk of not causing >> forward progress, after notify window time in a units of crystal clock, >> Notify VM exit will happen. Notify VM exit can happen incident to delivery >> of a vectored event. >> >> Expose a module param for configuring notify window, which is in unit of >> crystal clock cycle. >> - A negative value (e.g. -1) is to disable this feature. >> - Make the default as 0. It is safe because an internal threshold is added >> to notify window to ensure all the normal instructions being coverd. >> - User can set it to a large value when they want to give more cycles to >> wait for some reasons, e.g., silicon wrongly kill some normal instruction >> due to internal threshold is too small. >> >> Notify VM exit is defined in latest Intel Architecture Instruction Set >> Extensions Programming Reference, chapter 9.2. >> >> Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com> >> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> >> Signed-off-by: Tao Xu <tao3.xu@intel.com> >> --- >> >> Changelog: >> v2: >> Default set notify window to 0, less than 0 to disable. >> Add more description in commit message. > > Sorry if this was already discussed, but in case of nested > virtualization and when L1 also enables > SECONDARY_EXEC_NOTIFY_VM_EXITING, shouldn't we just reflect NOTIFY exits > during L2 execution to L1 instead of crashing the whole L1? > Notify VM Exit will not crash L1 guest if VM context valid in exit qualification. After VM exit, VMM can resume the guest normally. >> --- >> arch/x86/include/asm/vmx.h | 7 +++++ >> arch/x86/include/asm/vmxfeatures.h | 1 + >> arch/x86/include/uapi/asm/vmx.h | 4 ++- >> arch/x86/kvm/vmx/capabilities.h | 6 +++++ >> arch/x86/kvm/vmx/vmx.c | 42 ++++++++++++++++++++++++++++-- >> include/uapi/linux/kvm.h | 2 ++ >> 6 files changed, 59 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h >> index 0ffaa3156a4e..9104c85a973f 100644 >> --- a/arch/x86/include/asm/vmx.h >> +++ b/arch/x86/include/asm/vmx.h >> @@ -74,6 +74,7 @@ >> #define SECONDARY_EXEC_TSC_SCALING VMCS_CONTROL_BIT(TSC_SCALING) >> #define SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE VMCS_CONTROL_BIT(USR_WAIT_PAUSE) >> #define SECONDARY_EXEC_BUS_LOCK_DETECTION VMCS_CONTROL_BIT(BUS_LOCK_DETECTION) >> +#define SECONDARY_EXEC_NOTIFY_VM_EXITING VMCS_CONTROL_BIT(NOTIFY_VM_EXITING) >> >> #define PIN_BASED_EXT_INTR_MASK VMCS_CONTROL_BIT(INTR_EXITING) >> #define PIN_BASED_NMI_EXITING VMCS_CONTROL_BIT(NMI_EXITING) >> @@ -269,6 +270,7 @@ enum vmcs_field { >> SECONDARY_VM_EXEC_CONTROL = 0x0000401e, >> PLE_GAP = 0x00004020, >> PLE_WINDOW = 0x00004022, >> + NOTIFY_WINDOW = 0x00004024, >> VM_INSTRUCTION_ERROR = 0x00004400, >> VM_EXIT_REASON = 0x00004402, >> VM_EXIT_INTR_INFO = 0x00004404, >> @@ -555,6 +557,11 @@ enum vm_entry_failure_code { >> #define EPT_VIOLATION_EXECUTABLE (1 << EPT_VIOLATION_EXECUTABLE_BIT) >> #define EPT_VIOLATION_GVA_TRANSLATED (1 << EPT_VIOLATION_GVA_TRANSLATED_BIT) >> >> +/* >> + * Exit Qualifications for NOTIFY VM EXIT >> + */ >> +#define NOTIFY_VM_CONTEXT_INVALID BIT(0) >> + >> /* >> * VM-instruction error numbers >> */ >> diff --git a/arch/x86/include/asm/vmxfeatures.h b/arch/x86/include/asm/vmxfeatures.h >> index d9a74681a77d..15f0f2ab4f95 100644 >> --- a/arch/x86/include/asm/vmxfeatures.h >> +++ b/arch/x86/include/asm/vmxfeatures.h >> @@ -84,5 +84,6 @@ >> #define VMX_FEATURE_USR_WAIT_PAUSE ( 2*32+ 26) /* Enable TPAUSE, UMONITOR, UMWAIT in guest */ >> #define VMX_FEATURE_ENCLV_EXITING ( 2*32+ 28) /* "" VM-Exit on ENCLV (leaf dependent) */ >> #define VMX_FEATURE_BUS_LOCK_DETECTION ( 2*32+ 30) /* "" VM-Exit when bus lock caused */ >> +#define VMX_FEATURE_NOTIFY_VM_EXITING ( 2*32+ 31) /* VM-Exit when no event windows after notify window */ >> >> #endif /* _ASM_X86_VMXFEATURES_H */ >> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h >> index 946d761adbd3..ef4c80f6553e 100644 >> --- a/arch/x86/include/uapi/asm/vmx.h >> +++ b/arch/x86/include/uapi/asm/vmx.h >> @@ -91,6 +91,7 @@ >> #define EXIT_REASON_UMWAIT 67 >> #define EXIT_REASON_TPAUSE 68 >> #define EXIT_REASON_BUS_LOCK 74 >> +#define EXIT_REASON_NOTIFY 75 >> >> #define VMX_EXIT_REASONS \ >> { EXIT_REASON_EXCEPTION_NMI, "EXCEPTION_NMI" }, \ >> @@ -153,7 +154,8 @@ >> { EXIT_REASON_XRSTORS, "XRSTORS" }, \ >> { EXIT_REASON_UMWAIT, "UMWAIT" }, \ >> { EXIT_REASON_TPAUSE, "TPAUSE" }, \ >> - { EXIT_REASON_BUS_LOCK, "BUS_LOCK" } >> + { EXIT_REASON_BUS_LOCK, "BUS_LOCK" }, \ >> + { EXIT_REASON_NOTIFY, "NOTIFY"} >> >> #define VMX_EXIT_REASON_FLAGS \ >> { VMX_EXIT_REASONS_FAILED_VMENTRY, "FAILED_VMENTRY" } >> diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h >> index 8dee8a5fbc17..8527f34a84ac 100644 >> --- a/arch/x86/kvm/vmx/capabilities.h >> +++ b/arch/x86/kvm/vmx/capabilities.h >> @@ -407,4 +407,10 @@ static inline u64 vmx_supported_debugctl(void) >> return debugctl; >> } >> >> +static inline bool cpu_has_notify_vm_exiting(void) >> +{ >> + return vmcs_config.cpu_based_2nd_exec_ctrl & >> + SECONDARY_EXEC_NOTIFY_VM_EXITING; >> +} >> + >> #endif /* __KVM_X86_VMX_CAPS_H */ >> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >> index 4bceb5ca3a89..c0ad01c88dac 100644 >> --- a/arch/x86/kvm/vmx/vmx.c >> +++ b/arch/x86/kvm/vmx/vmx.c >> @@ -205,6 +205,10 @@ module_param(ple_window_max, uint, 0444); >> int __read_mostly pt_mode = PT_MODE_SYSTEM; >> module_param(pt_mode, int, S_IRUGO); >> >> +/* Default is 0, less than 0 (for example, -1) disables notify window. */ >> +static int __read_mostly notify_window; >> +module_param(notify_window, int, 0644); >> + >> static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush); >> static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_cond); >> static DEFINE_MUTEX(vmx_l1d_flush_mutex); >> @@ -2539,7 +2543,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf, >> SECONDARY_EXEC_PT_USE_GPA | >> SECONDARY_EXEC_PT_CONCEAL_VMX | >> SECONDARY_EXEC_ENABLE_VMFUNC | >> - SECONDARY_EXEC_BUS_LOCK_DETECTION; >> + SECONDARY_EXEC_BUS_LOCK_DETECTION | >> + SECONDARY_EXEC_NOTIFY_VM_EXITING; >> if (cpu_has_sgx()) >> opt2 |= SECONDARY_EXEC_ENCLS_EXITING; >> if (adjust_vmx_controls(min2, opt2, >> @@ -4376,6 +4381,9 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx) >> if (!vcpu->kvm->arch.bus_lock_detection_enabled) >> exec_control &= ~SECONDARY_EXEC_BUS_LOCK_DETECTION; >> >> + if (cpu_has_notify_vm_exiting() && notify_window < 0) >> + exec_control &= ~SECONDARY_EXEC_NOTIFY_VM_EXITING; >> + >> vmx->secondary_exec_control = exec_control; >> } >> >> @@ -4423,6 +4431,9 @@ static void init_vmcs(struct vcpu_vmx *vmx) >> vmx->ple_window_dirty = true; >> } >> >> + if (cpu_has_notify_vm_exiting() && notify_window >= 0) >> + vmcs_write32(NOTIFY_WINDOW, notify_window); >> + >> vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, 0); >> vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, 0); >> vmcs_write32(CR3_TARGET_COUNT, 0); /* 22.2.1 */ >> @@ -5642,6 +5653,31 @@ static int handle_bus_lock_vmexit(struct kvm_vcpu *vcpu) >> return 0; >> } >> >> +static int handle_notify(struct kvm_vcpu *vcpu) >> +{ >> + unsigned long exit_qual = vmx_get_exit_qual(vcpu); >> + >> + if (!(exit_qual & NOTIFY_VM_CONTEXT_INVALID)) { >> + /* >> + * Notify VM exit happened while executing iret from NMI, >> + * "blocked by NMI" bit has to be set before next VM entry. >> + */ >> + if (enable_vnmi && >> + (exit_qual & INTR_INFO_UNBLOCK_NMI)) >> + vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO, >> + GUEST_INTR_STATE_NMI); >> + >> + return 1; >> + } >> + >> + vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; >> + vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_NO_EVENT_WINDOW; >> + vcpu->run->internal.ndata = 1; >> + vcpu->run->internal.data[0] = exit_qual; >> + >> + return 0; >> +} >> + >> /* >> * The exit handlers return 1 if the exit was handled fully and guest execution >> * may resume. Otherwise they set the kvm_run parameter to indicate what needs >> @@ -5699,6 +5735,7 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = { >> [EXIT_REASON_PREEMPTION_TIMER] = handle_preemption_timer, >> [EXIT_REASON_ENCLS] = handle_encls, >> [EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit, >> + [EXIT_REASON_NOTIFY] = handle_notify, >> }; >> >> static const int kvm_vmx_max_exit_handlers = >> @@ -6042,7 +6079,8 @@ static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath) >> exit_reason.basic != EXIT_REASON_EPT_VIOLATION && >> exit_reason.basic != EXIT_REASON_PML_FULL && >> exit_reason.basic != EXIT_REASON_APIC_ACCESS && >> - exit_reason.basic != EXIT_REASON_TASK_SWITCH)) { >> + exit_reason.basic != EXIT_REASON_TASK_SWITCH && >> + exit_reason.basic != EXIT_REASON_NOTIFY)) { >> int ndata = 3; >> >> vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; >> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h >> index 3fd9a7e9d90c..bb3b49b1fb0d 100644 >> --- a/include/uapi/linux/kvm.h >> +++ b/include/uapi/linux/kvm.h >> @@ -278,6 +278,8 @@ struct kvm_xen_exit { >> #define KVM_INTERNAL_ERROR_DELIVERY_EV 3 >> /* Encounter unexpected vm-exit reason */ >> #define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4 >> +/* Encounter notify vm-exit */ >> +#define KVM_INTERNAL_ERROR_NO_EVENT_WINDOW 5 >> >> /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */ >> struct kvm_run { >
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