> perf/x86/intel/pt: Introduce a new function to get capability of Intel PT
>
> Subjects should be short and consice.
>
> perf/x86/intel/pt: Introduce intel_pt_cap_decode()
>
> Also the decsription in $subject is not what the description below says. Please make sure that your subjects and changelogs are consistent.
>
> > New function pt_cap_decode() will be invoked in KVM to check if a
> > specific capability is available 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.
>
> Again it took me a while to figure out what you are trying to say. Suggestion:
>
> intel_pt_validate_cap() validates whether a given PT capability is
> supported by the hardware. It checks the PT capability array which
> reflects the capabilites of the hardware on which the code is executed.
>
> For setting up PT for KVM guests this is not correct as the capability
> array for the guest can be different from the host array.
>
> Provide a new function to check against a given capability array.
>
Thanks for your suggestion. It looks good to me.
> > -u32 pt_cap_get(enum pt_capabilities cap)
> > +u32 pt_cap_decode(u32 *caps, enum pt_capabilities capability)
>
> > {
> > - struct pt_cap_desc *cd = &pt_caps[cap];
> > - u32 c = pt_pmu.caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
> > + struct pt_cap_desc *cd = &pt_caps[capability];
> > + u32 c = caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
> > unsigned int shift = __ffs(cd->mask);
> >
> > return (c & cd->mask) >> shift;
> > }
> > +EXPORT_SYMBOL_GPL(pt_cap_decode);
> > +
> > +u32 pt_cap_get(enum pt_capabilities cap) {
> > + return pt_cap_decode(pt_pmu.caps, cap); }
> > EXPORT_SYMBOL_GPL(pt_cap_get);
>
> pt_cap_decode() is yet another misnomer.
>
> So what you really want is:
>
> s/pt_cap_get()/intel_pt_validate_hw_cap()/
>
> and the new function wants to be:
>
> intel_pt_validate_cap()
>
> So it's entirely clear from the naming that the former pt_cap_get() is related to the hardware capabilities of the machine on which the code
> is executing.
>
Will be fixed it next version.
Thanks,
Luwei Kang
