Re: [PATCH v7 05/13] perf/x86/intel/pt: Introduce a new function to get capability of Intel PT

[Paolo Bonzini]

On 03/05/2018 14:30, Kang, Luwei wrote:
>> Can you elaborate on this, what information do we need besides
>> MSR_IA32_VMX_MISC[14]?
>
> Enable Intel PT in guest depend on SECONDARY_EXEC_PT_USE_GPA, EPT,
> MSR_IA32_VMX_MISC[14] and the capability of " PT_CAP_topa_output" on
> hardware. PT driver will return " -ENODEV" if hardware not support
> "PT_CAP_topa_output".

I actually don't understand why PT_CAP_topa_output matters for the
purpose of enabling PT in the guest.  However you still need
__pt_cap_get() in the CPUID checks.

Paolo