RE: [PATCH v5 04/18] xen/cpufreq: introduce new sub-hypercall to propagate CPPC data

["Penny, Zheng" <penny.zheng@xxxxxxx>]

[Public]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Thursday, June 12, 2025 12:10 AM
> To: Penny, Zheng <penny.zheng@xxxxxxx>
> Cc: Huang, Ray <Ray.Huang@xxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>;
> Anthony PERARD <anthony.perard@xxxxxxxxxx>; Orzel, Michal
> <Michal.Orzel@xxxxxxx>; Julien Grall <julien@xxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v5 04/18] xen/cpufreq: introduce new sub-hypercall to
> propagate CPPC data
>
> On 27.05.2025 10:48, Penny Zheng wrote:
> > @@ -635,6 +641,124 @@ out:
> >      return ret;
> >  }
> >
> > +static void print_CPPC(const struct xen_processor_cppc *cppc_data) {
> > +    printk("\t_CPC: highest_perf=%u, lowest_perf=%u, "
> > +           "nominal_perf=%u, lowest_nonlinear_perf=%u, "
> > +           "nominal_mhz=%uMHz, lowest_mhz=%uMHz\n",
> > +           cppc_data->cpc.highest_perf, cppc_data->cpc.lowest_perf,
> > +           cppc_data->cpc.nominal_perf, 
> > cppc_data->cpc.lowest_nonlinear_perf,
> > +           cppc_data->cpc.nominal_mhz, cppc_data->cpc.lowest_mhz); }
> > +
> > +int set_cppc_pminfo(unsigned int acpi_id,
> > +                    const struct xen_processor_cppc *cppc_data) {
> > +    int ret = 0, cpuid;
> > +    struct processor_pminfo *pm_info;
> > +
> > +    cpuid = get_cpu_id(acpi_id);
> > +    if ( cpuid < 0 || !cppc_data )
>
> The !cppc_data part isn't really needed, is it?

I added it because set_cppc_pminfo() is an external function, and maybe we 
shall validate each
input for any external functions? Or maybe not. I'm not sure if it is a MUST?

>
> > +        pm_info->init = XEN_CPPC_INIT;
> > +        ret = cpufreq_cpu_init(cpuid); #ifndef NDEBUG
> > +        if ( ret )
> > +            dprintk(XENLOG_WARNING,
> > +                    "CPU %u failed to be initialized with amd-cppc mode, 
> > and users
> could only reboot and re-define cmdline with \"cpufreq=xen\"",
> > +                    cpuid);
> > +#endif
>
> What use if the #ifdef here? The more that NDEBUG controls behavior of
> ASSERT(), not that of (debug) logging.
>

Understood. Maybe I shall use one-time printk_once()

>
> Jan