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SubjectRe: [PATCH v3 7/9] KVM: x86: Implement Intel Processor Trace MSRs read/write
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On 01/12/2017 07:40, Kang, Luwei wrote:
>>> + case MSR_IA32_RTIT_ADDR0_A ... MSR_IA32_RTIT_ADDR3_B: {
>>> + u32 eax, ebx, ecx, edx;
>>> +
>>> + cpuid_count(0x14, 1, &eax, &ebx, &ecx, &edx);
>>
>> Please cache the cpuid_count result, or do the cpuid_count after testing
>> vmx_pt_supported() (which you can use instead of going through kvm_x86_ops).
>
> Hi Paolo,
> Thanks for your reply. I have cache EAX in "struct pt_desc" and will initialize in vmx_vcpu_setup().
> +struct pt_desc {
> + unsigned int addr_num;
> + struct pt_ctx host;
> + struct pt_ctx guest;
> +};
> But kvm_init_msr_list() is invoked too early, I have to read from hardware. So, what about change like this.
>
> - cpuid_count(0x14, 1, &eax, &ebx, &ecx, &edx);
> - if (!kvm_x86_ops->pt_supported() || msrs_to_save[i] -
> - MSR_IA32_RTIT_ADDR0_A >= (eax & 0x7))
> + if (!kvm_x86_ops->pt_supported())
> continue;
> + cpuid_count(0x14, 1, &eax, &ebx, &ecx, &edx);
> + if (msrs_to_save[i] -
> + MSR_IA32_RTIT_ADDR0_A >= (eax & 0x7))
> + continue;

For kvm_init_msr_list it's okay. But can you please add a
pt_msr_count() function?

Thanks,

Paolo

> Thanks,
> Luwei Kang
>
>>
>> Thanks,
>>
>> Paolo
>>
>>> + if (!kvm_x86_ops->pt_supported() || msrs_to_save[i] -
>>> + MSR_IA32_RTIT_ADDR0_A >= (eax & 0x7))
>>> + continue;
>>> + break;
>

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