>
>> /*
>> * Use nested page tables by default. Note, NPT may get forced off by
>> * svm_hardware_setup() if it's unsupported by hardware or the host kernel.
>> @@ -3231,6 +3234,19 @@ static int invpcid_interception(struct kvm_vcpu *vcpu)
>> return kvm_handle_invpcid(vcpu, type, gva);
>> }
>>
>> +static int bus_lock_exit(struct kvm_vcpu *vcpu)
>> +{
>> + struct vcpu_svm *svm = to_svm(vcpu);
>> +
>> + vcpu->run->exit_reason = KVM_EXIT_X86_BUS_LOCK;
>> + vcpu->run->flags |= KVM_RUN_X86_BUS_LOCK;
>> +
>> + /* Reload the counter again */
>> + svm->vmcb->control.bus_lock_counter = bus_lock_counter;
>> +
>> + return 0;
>> +}
>> +
>> static int (*const svm_exit_handlers[])(struct kvm_vcpu *vcpu) = {
>> [SVM_EXIT_READ_CR0] = cr_interception,
>> [SVM_EXIT_READ_CR3] = cr_interception,
>> @@ -3298,6 +3314,7 @@ static int (*const svm_exit_handlers[])(struct kvm_vcpu *vcpu) = {
>> [SVM_EXIT_CR4_WRITE_TRAP] = cr_trap,
>> [SVM_EXIT_CR8_WRITE_TRAP] = cr_trap,
>> [SVM_EXIT_INVPCID] = invpcid_interception,
>> + [SVM_EXIT_BUS_LOCK] = bus_lock_exit,
>> [SVM_EXIT_NPF] = npf_interception,
>> [SVM_EXIT_RSM] = rsm_interception,
>> [SVM_EXIT_AVIC_INCOMPLETE_IPI] = avic_incomplete_ipi_interception,
>> @@ -4356,6 +4373,27 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
>
> Why on earth is this in svm_vcpu_after_set_cpuid()? This has nothing to do with
> guest CPUID.>
Sorry, my bad. I will move it to init_vmcb().
>> set_msr_interception(vcpu, svm->msrpm, MSR_IA32_FLUSH_CMD, 0,
>> !!guest_cpuid_has(vcpu, X86_FEATURE_FLUSH_L1D));
>>
>> + if (cpu_feature_enabled(X86_FEATURE_BUS_LOCK_THRESHOLD) &&
>
> This should be a slow path, there's zero reason to check for host support as
> bus_lock_detection_enabled should be allowed if and only if it's supported.>
Agreed. I will remove this check.
>> + vcpu->kvm->arch.bus_lock_detection_enabled) {
>> + svm_set_intercept(svm, INTERCEPT_BUSLOCK);
>> +
>> + /*
>> + * The CPU decrements the bus lock counter every time a bus lock
>> + * is detected. Once the counter reaches zero a VMEXIT_BUSLOCK
>> + * is generated. A value of zero for bus lock counter means a
>> + * VMEXIT_BUSLOCK at every bus lock detection.
>> + *
>> + * Currently, default value for bus_lock_counter is set to 10.
>
> Please don't document the default _here_. Because inevitably this will become
> stale when the default changes.
>
Ack.
>> + * So, the VMEXIT_BUSLOCK is generated after every 10 bus locks
>> + * detected.
>> + */
>> + svm->vmcb->control.bus_lock_counter = bus_lock_counter;
>> + pr_debug("Setting buslock counter to %u\n", bus_lock_counter);
>> + } else {
>> + svm_clr_intercept(svm, INTERCEPT_BUSLOCK);
>> + svm->vmcb->control.bus_lock_counter = 0;
>> + }
>> +
>> if (sev_guest(vcpu->kvm))
>> sev_vcpu_after_set_cpuid(svm);
>>
>> @@ -5149,6 +5187,11 @@ static __init void svm_set_cpu_caps(void)
>> kvm_cpu_cap_set(X86_FEATURE_SVME_ADDR_CHK);
>> }
>>
>> + if (cpu_feature_enabled(X86_FEATURE_BUS_LOCK_THRESHOLD)) {
>> + pr_info("Bus Lock Threashold supported\n");
>> + kvm_caps.has_bus_lock_exit = true;
>> + }
>> +
>> /* CPUID 0x80000008 */
>> if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) ||
>> boot_cpu_has(X86_FEATURE_AMD_SSBD))
>> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
>> index d80a4c6b5a38..2a77232105da 100644
>> --- a/arch/x86/kvm/x86.h
>> +++ b/arch/x86/kvm/x86.h
>> @@ -58,6 +58,7 @@ void kvm_spurious_fault(void);
>> #define KVM_VMX_DEFAULT_PLE_WINDOW_MAX UINT_MAX
>> #define KVM_SVM_DEFAULT_PLE_WINDOW_MAX USHRT_MAX
>> #define KVM_SVM_DEFAULT_PLE_WINDOW 3000
>> +#define KVM_SVM_DEFAULT_BUS_LOCK_COUNTER 10
>
> There's zero reason this needs to be in x86.h. I don't even see a reason to
> have a #define, there's literally one user.
Yeah. I agree. I remove it from V2.
- Manali
