On 17.06.2025 06:18, Penny, Zheng wrote:
> [Public]
>
>> -----Original Message-----
>> From: Jan Beulich <jbeul...@suse.com>
>> Sent: Thursday, June 12, 2025 12:10 AM
>> To: Penny, Zheng <penny.zh...@amd.com>
>> Cc: Huang, Ray <ray.hu...@amd.com>; Andrew Cooper
>> <andrew.coop...@citrix.com>; Roger Pau Monné <roger....@citrix.com>;
>> Anthony PERARD <anthony.per...@vates.tech>; Orzel, Michal
>> <michal.or...@amd.com>; Julien Grall <jul...@xen.org>; Stefano Stabellini
>> <sstabell...@kernel.org>; xen-devel@lists.xenproject.org
>> 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?
It's not. If look through code globally, it is rare that we have such checks.
Many of them are imo pointless (and thus giving bad examples). In certain
cases they're meaningful to have.
>>> + 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()
Perhaps, also considering that the action to take is relevant also in
release builds. However, "users could only" is once again odd wording for
a log message. How about "CPU%u failed amd-cppc mode init; use \"cpufreq=xen\"
instead"?
Jan
