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Date: Mon, 14 Sep 2020 17:32:11 +0800
From: Chenyi Qiang <chenyi.qiang@...el.com>
To: Sean Christopherson <sean.j.christopherson@...el.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
Xiaoyao Li <xiaoyao.li@...el.com>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC v3 2/2] KVM: VMX: Enable bus lock VM exit
Thank you for comments. Will clean up my code.
On 9/12/2020 1:27 AM, Sean Christopherson wrote:
> On Thu, Sep 10, 2020 at 04:37:51PM +0800, Chenyi Qiang wrote:
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 5303dbc5c9bc..8059b8b21ecd 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -961,6 +961,9 @@ struct kvm_arch {
>> bool guest_can_read_msr_platform_info;
>> bool exception_payload_enabled;
>>
>> + /* Set when bus lock vm exit is enabled by user */
>> + bool bus_lock_exit;
>
> Maybe bus_lock_detection_enabled? Then you don't need the comment or the
> accessor.
>
>> +
>> struct kvm_pmu_event_filter *pmu_event_filter;
>> struct task_struct *nx_lpage_recovery_thread;
>> };
>> @@ -1347,6 +1350,8 @@ extern u8 kvm_tsc_scaling_ratio_frac_bits;
>> extern u64 kvm_max_tsc_scaling_ratio;
>> /* 1ull << kvm_tsc_scaling_ratio_frac_bits */
>> extern u64 kvm_default_tsc_scaling_ratio;
>> +/* bus lock detection supported */
>> +extern bool kvm_has_bus_lock_exit;
>
> Hrm, it'd be nice to somehow squeeze this into kvm_cpu_caps, but I can't
> think of a clever/clean way to do so.
>
>> extern u64 kvm_mce_cap_supported;
>>
>> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
>> index cd7de4b401fe..93a880bc31a7 100644
>> --- a/arch/x86/include/asm/vmx.h
>> +++ b/arch/x86/include/asm/vmx.h
>> @@ -73,6 +73,7 @@
>> #define SECONDARY_EXEC_PT_USE_GPA VMCS_CONTROL_BIT(PT_USE_GPA)
>> #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 PIN_BASED_EXT_INTR_MASK VMCS_CONTROL_BIT(INTR_EXITING)
>> #define PIN_BASED_NMI_EXITING VMCS_CONTROL_BIT(NMI_EXITING)
>> diff --git a/arch/x86/include/asm/vmxfeatures.h b/arch/x86/include/asm/vmxfeatures.h
>> index 9915990fd8cf..e80523346274 100644
>> --- a/arch/x86/include/asm/vmxfeatures.h
>> +++ b/arch/x86/include/asm/vmxfeatures.h
>> @@ -83,5 +83,6 @@
>> #define VMX_FEATURE_TSC_SCALING ( 2*32+ 25) /* Scale hardware TSC when read in guest */
>> #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 */
>>
>> #endif /* _ASM_X86_VMXFEATURES_H */
>> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
>> index 0780f97c1850..a1471c05f7f9 100644
>> --- a/arch/x86/include/uapi/asm/kvm.h
>> +++ b/arch/x86/include/uapi/asm/kvm.h
>> @@ -111,6 +111,7 @@ struct kvm_ioapic_state {
>> #define KVM_NR_IRQCHIPS 3
>>
>> #define KVM_RUN_X86_SMM (1 << 0)
>> +#define KVM_RUN_BUS_LOCK (1 << 1)
>>
>> /* for KVM_GET_REGS and KVM_SET_REGS */
>> struct kvm_regs {
>> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
>> index b8ff9e8ac0d5..14c177c4afd5 100644
>> --- a/arch/x86/include/uapi/asm/vmx.h
>> +++ b/arch/x86/include/uapi/asm/vmx.h
>> @@ -88,6 +88,7 @@
>> #define EXIT_REASON_XRSTORS 64
>> #define EXIT_REASON_UMWAIT 67
>> #define EXIT_REASON_TPAUSE 68
>> +#define EXIT_REASON_BUS_LOCK 74
>>
>> #define VMX_EXIT_REASONS \
>> { EXIT_REASON_EXCEPTION_NMI, "EXCEPTION_NMI" }, \
>> @@ -148,7 +149,8 @@
>> { EXIT_REASON_XSAVES, "XSAVES" }, \
>> { EXIT_REASON_XRSTORS, "XRSTORS" }, \
>> { EXIT_REASON_UMWAIT, "UMWAIT" }, \
>> - { EXIT_REASON_TPAUSE, "TPAUSE" }
>> + { EXIT_REASON_TPAUSE, "TPAUSE" }, \
>> + { EXIT_REASON_BUS_LOCK, "BUS_LOCK" }
>>
>> #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 4bbd8b448d22..aa94535e6705 100644
>> --- a/arch/x86/kvm/vmx/capabilities.h
>> +++ b/arch/x86/kvm/vmx/capabilities.h
>> @@ -262,6 +262,12 @@ static inline bool cpu_has_vmx_tsc_scaling(void)
>> SECONDARY_EXEC_TSC_SCALING;
>> }
>>
>> +static inline bool cpu_has_vmx_bus_lock_detection(void)
>> +{
>> + return vmcs_config.cpu_based_2nd_exec_ctrl &
>> + SECONDARY_EXEC_BUS_LOCK_DETECTION;
>> +}
>> +
>> static inline bool cpu_has_vmx_apicv(void)
>> {
>> return cpu_has_vmx_apic_register_virt() &&
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index adc59cf9036d..5dbfee639375 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -2461,7 +2461,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>> SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE |
>> SECONDARY_EXEC_PT_USE_GPA |
>> SECONDARY_EXEC_PT_CONCEAL_VMX |
>> - SECONDARY_EXEC_ENABLE_VMFUNC;
>> + SECONDARY_EXEC_ENABLE_VMFUNC |
>> + SECONDARY_EXEC_BUS_LOCK_DETECTION;
>> if (cpu_has_sgx())
>> opt2 |= SECONDARY_EXEC_ENCLS_EXITING;
>> if (adjust_vmx_controls(min2, opt2,
>> @@ -4244,6 +4245,9 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
>> }
>> }
>>
>> + if (!kvm_bus_lock_exit_enabled(vmx->vcpu.kvm))
>> + exec_control &= ~SECONDARY_EXEC_BUS_LOCK_DETECTION;
>> +
>> vmx->secondary_exec_control = exec_control;
>> }
>>
>> @@ -5685,6 +5689,14 @@ static int handle_encls(struct kvm_vcpu *vcpu)
>> return 1;
>> }
>>
>> +static int handle_bus_lock(struct kvm_vcpu *vcpu)
>> +{
>> + struct kvm_run *kvm_run = vcpu->run;
>> +
>> + kvm_run->exit_reason = KVM_EXIT_BUS_LOCK;
>
> No need for kvm_run, "vcpu->run->exit_reason = KVM_EXIT_BUS_LOCK" will do.
>
>> + 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
>> @@ -5741,6 +5753,7 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
>> [EXIT_REASON_VMFUNC] = handle_vmx_instruction,
>> [EXIT_REASON_PREEMPTION_TIMER] = handle_preemption_timer,
>> [EXIT_REASON_ENCLS] = handle_encls,
>> + [EXIT_REASON_BUS_LOCK] = handle_bus_lock,
>> };
>>
>> static const int kvm_vmx_max_exit_handlers =
>> @@ -5979,7 +5992,7 @@ void dump_vmcs(void)
>> * The guest has exited. See if we can fix it or if we need userspace
>> * assistance.
>> */
>> -static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>> +static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>> {
>> struct vcpu_vmx *vmx = to_vmx(vcpu);
>> union vmx_exit_reason exit_reason = vmx->exit_reason;
>> @@ -6131,6 +6144,28 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>> return 0;
>> }
>>
>> +static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>> +{
>> + struct vcpu_vmx *vmx = to_vmx(vcpu);
>
> Personal preference, but I'd probably skip the local 'vmx' variable since
> there's only a single user, i.e. "to_vmx(vcpu)->exit_reason....".
>
>> + int ret = __vmx_handle_exit(vcpu, exit_fastpath);
>> +
>> + /*
>> + * Even when current exit reason is handled by KVM
>> + * internally, we still needs to exit to user space
>> + * when bus lock detected to inform that there is a
>> + * bus lock in guest.
>
> Run these lines out to the edge of 80 chars, wrapping this aggressively just
> adds extra lines.
>
>> + */
>> + if (vmx->exit_reason.bus_lock_detected) {
>> + if (ret > 0)
>> + vcpu->run->exit_reason = KVM_EXIT_BUS_LOCK;
>> + else
>> + vcpu->run->flags |= KVM_RUN_BUS_LOCK;
>> + return 0;
>> + }
>> + vcpu->run->flags &= ~KVM_RUN_BUS_LOCK;
>> + return ret;
>> +}
>> +
>> /*
>> * Software based L1D cache flush which is used when microcode providing
>> * the cache control MSR is not loaded.
>> @@ -8097,6 +8132,9 @@ static __init int hardware_setup(void)
>> kvm_tsc_scaling_ratio_frac_bits = 48;
>> }
>>
>> + if (cpu_has_vmx_bus_lock_detection())
>> + kvm_has_bus_lock_exit = true;
>
> Or simply:
>
> kvm_has_bus_lock_exit = cpu_has_vmx_bus_lock_detection();
>
>
>> +
>> set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */
>>
>> if (enable_ept)
>> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
>> index 8bf97a81affd..779ea3b15134 100644
>> --- a/arch/x86/kvm/vmx/vmx.h
>> +++ b/arch/x86/kvm/vmx/vmx.h
>> @@ -105,7 +105,7 @@ union vmx_exit_reason {
>> u32 reserved23 : 1;
>> u32 reserved24 : 1;
>> u32 reserved25 : 1;
>> - u32 reserved26 : 1;
>> + u32 bus_lock_detected : 1;
>> u32 enclave_mode : 1;
>> u32 smi_pending_mtf : 1;
>> u32 smi_from_vmx_root : 1;
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index d39d6cf1d473..d96619ce7f66 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -134,6 +134,8 @@ u64 __read_mostly kvm_max_tsc_scaling_ratio;
>> EXPORT_SYMBOL_GPL(kvm_max_tsc_scaling_ratio);
>> u64 __read_mostly kvm_default_tsc_scaling_ratio;
>> EXPORT_SYMBOL_GPL(kvm_default_tsc_scaling_ratio);
>> +bool __read_mostly kvm_has_bus_lock_exit;
>> +EXPORT_SYMBOL_GPL(kvm_has_bus_lock_exit);
>>
>> /* tsc tolerance in parts per million - default to 1/2 of the NTP threshold */
>> static u32 __read_mostly tsc_tolerance_ppm = 250;
>> @@ -3578,6 +3580,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>> case KVM_CAP_SMALLER_MAXPHYADDR:
>> r = (int) allow_smaller_maxphyaddr;
>> break;
>> + case KVM_CAP_X86_BUS_LOCK_EXIT:
>
> Hmm, it might make more sense to do:
>
> if (kvm_has_bus_lock_exit)
> r = KVM_BUS_LOCK_DETECTION_OFF |
> KVM_BUS_LOCK_DETECTION_EXIT;
> else
> r = 0;
>
> On the other hand I can see it being useful for userspace to know that
> KVM itself supports bus lock detection, but hardware does not.
>
>> + r |= KVM_BUS_LOCK_DETECTION_OFF;
>> + if (kvm_has_bus_lock_exit)
>> + r |= KVM_BUS_LOCK_DETECTION_EXIT;
>> + break;
>> default:
>> break;
>> }
>> @@ -5030,6 +5037,20 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
>> kvm->arch.exception_payload_enabled = cap->args[0];
>> r = 0;
>> break;
>> + case KVM_CAP_X86_BUS_LOCK_EXIT:
>> + r = -EINVAL;
>> + if (cap->args[0] & ~KVM_BUS_LOCK_DETECTION_VALID_MODE)
>> + break;
>> +
>> + if ((cap->args[0] & KVM_BUS_LOCK_DETECTION_OFF) &&
>> + (cap->args[0] & KVM_BUS_LOCK_DETECTION_EXIT))
>> + break;
>> +
>> + if (kvm_has_bus_lock_exit &&
>> + cap->args[0] & KVM_BUS_LOCK_DETECTION_EXIT)
>> + kvm->arch.bus_lock_exit = true;
>> + r = 0;
>> + break;
>> default:
>> r = -EINVAL;
>> break;
>> @@ -7772,12 +7793,16 @@ static void post_kvm_run_save(struct kvm_vcpu *vcpu)
>> struct kvm_run *kvm_run = vcpu->run;
>>
>> kvm_run->if_flag = (kvm_get_rflags(vcpu) & X86_EFLAGS_IF) != 0;
>> - kvm_run->flags = is_smm(vcpu) ? KVM_RUN_X86_SMM : 0;
>> kvm_run->cr8 = kvm_get_cr8(vcpu);
>> kvm_run->apic_base = kvm_get_apic_base(vcpu);
>> kvm_run->ready_for_interrupt_injection =
>> pic_in_kernel(vcpu->kvm) ||
>> kvm_vcpu_ready_for_interrupt_injection(vcpu);
>> +
>> + if (is_smm(vcpu))
>> + kvm_run->flags |= KVM_RUN_X86_SMM;
>> + else
>> + kvm_run->flags &= ~KVM_RUN_X86_SMM;
>> }
>>
>> static void update_cr8_intercept(struct kvm_vcpu *vcpu)
>> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
>> index 995ab696dcf0..54aa7712cb52 100644
>> --- a/arch/x86/kvm/x86.h
>> +++ b/arch/x86/kvm/x86.h
>> @@ -335,6 +335,11 @@ static inline bool kvm_cstate_in_guest(struct kvm *kvm)
>> return kvm->arch.cstate_in_guest;
>> }
>>
>> +static inline bool kvm_bus_lock_exit_enabled(struct kvm *kvm)
>
> I don't see any point in adding an accessor for a bool.
>
>> +{
>> + return kvm->arch.bus_lock_exit;
>> +}
>> +
>> DECLARE_PER_CPU(struct kvm_vcpu *, current_vcpu);
>>
>> static inline void kvm_before_interrupt(struct kvm_vcpu *vcpu)
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index f6d86033c4fa..3f0176733622 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -248,6 +248,7 @@ struct kvm_hyperv_exit {
>> #define KVM_EXIT_IOAPIC_EOI 26
>> #define KVM_EXIT_HYPERV 27
>> #define KVM_EXIT_ARM_NISV 28
>> +#define KVM_EXIT_BUS_LOCK 29
>>
>> /* For KVM_EXIT_INTERNAL_ERROR */
>> /* Emulate instruction failed. */
>> @@ -1035,6 +1036,7 @@ struct kvm_ppc_resize_hpt {
>> #define KVM_CAP_LAST_CPU 184
>> #define KVM_CAP_SMALLER_MAXPHYADDR 185
>> #define KVM_CAP_S390_DIAG318 186
>> +#define KVM_CAP_X86_BUS_LOCK_EXIT 187
>>
>> #ifdef KVM_CAP_IRQ_ROUTING
>>
>> @@ -1689,4 +1691,9 @@ struct kvm_hyperv_eventfd {
>> #define KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (1 << 0)
>> #define KVM_DIRTY_LOG_INITIALLY_SET (1 << 1)
>>
>> +#define KVM_BUS_LOCK_DETECTION_OFF (1 << 0)
>> +#define KVM_BUS_LOCK_DETECTION_EXIT (1 << 1)
>> +#define KVM_BUS_LOCK_DETECTION_VALID_MODE (KVM_BUS_LOCK_DETECTION_OFF | \
>> + KVM_BUS_LOCK_DETECTION_EXIT)
>
> I don't think we want to define KVM_BUS_LOCK_DETECTION_VALID_MODE in the
> uapi header, that should be kernel only.
>
>> +
>> #endif /* __LINUX_KVM_H */
>> --
>> 2.17.1
>>
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