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

[Kang, Luwei]

> > > > New function __pt_cap_get() will be invoked in KVM to check if a
> > > > specific capability is availiable in KVM guest.
> > > > Another function pt_cap_get() can only check the hardware
> > > > capabilities but this may different with KVM guest because some
> > > > features may not be exposed to guest.
> > >
> > > Do we really need both in KVM?
> >
> > Yes, KVM need get host capability to estimate if can expose this
> > feature to guest
> 
> 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".

Thanks,
Luwei Kang

> 
> Thanks,
> --
> Alex