Re: Warnings `Could not retrieve perf counters (-19)` and `amd_pstate: the _CPC object is not present in SBIOS or ACPI disabled` (Dell PowerEdge R7625, AMD EPYC 9174F)

[Mario Limonciello <mario.limonciello@amd.com>]

On 2/11/2025 10:12, Paul Menzel wrote:
> Dear Linux folks,
> 
> 
> Am 28.01.25 um 16:08 schrieb Paul Menzel:
>> [Cc: +x86 maintainers and ACPI list]
> 
>> Am 28.01.25 um 11:49 schrieb Paul Menzel:
>>
>>> Thank you for your quick replies. Gautham, messages with HTML are 
>>> rejected by Linux kernel lists.
>>>
>>>
>>> Am 28.01.25 um 04:51 schrieb Shenoy, Gautham Ranjal:
>>>
>>>> As Mario mentioned, you need to enable the CPPC option. Looking for 
>>>> some of the Dell PowerEdge documentation, there is an option called 
>>>> "Collaborative CPU Performance Control" (https://www.dell.com/ 
>>>> support/manuals/en-in/poweredge-r730/r730_ompublication/system- 
>>>> profile-settings-details?guid=guid-2e9b46a1-71e3-4072-9d86- 
>>>> db648757f0e6&lang=en-us).
>>>>
>>>> [cid:fe57df8f-3d99-4ea0-8f6e-b0daae49bb0e]
>>>> Can you please try enabling it ?
>>>
>>> You quoted the Dell PowerEdge R730. I couldn’t find it in the *Dell 
>>> PowerEdge R7625 Installation and Service Manual* [1], and also it’s 
>>> not listed in the iDRAC9 Web site (attached with added `.txt` 
>>> extension to trick the Linux list).
>>
>> The amd_pstate warning seems to be related to the perf counters 
>> warning Linux prints earlier:
>>
>>      $ dmesg --level alert,crit,err,warn
>>      [    2.666393] Spectre V2 : WARNING: Unprivileged eBPF is enabled 
>> with eIBRS on, data leaks possible via Spectre v2 BHB attacks!
>>      [    8.109446] Could not retrieve perf counters (-19)
>>      [    9.386551] scsi 0:0:4:0: set ignore_delay_remove for 
>> handle(0x0012)
>>      [    9.487804] amd_pstate: the _CPC object is not present in 
>> SBIOS or ACPI disabled
>>      [   14.726193] wmi_bus wmi_bus-PNP0C14:00: [Firmware Bug]: WQBC 
>> data block query control method not found
>>
>> x86 maintainers, the original report with the Linux logs attached is 
>> in the archive [3].
>>
>> It looks like, there is something missing in the Dell firmware to 
>> enable the feature.
>>
>> The perf counters warning is from `amd_set_max_freq_ratio()` in `arch/ 
>> x86/kernel/acpi/cppc.c`:
>>
>> ```
>> static void amd_set_max_freq_ratio(void)
>> {
>>          struct cppc_perf_caps perf_caps;
>>          u64 numerator, nominal_perf;
>>          u64 perf_ratio;
>>          int rc;
>>
>>          rc = cppc_get_perf_caps(0, &perf_caps);
>>          if (rc) {
>>                  pr_warn("Could not retrieve perf counters (%d)\n", rc);
>>                  return;
>>          }
>>          […]
>> }
>> ```
>>
>> With
>>
>>      include/uapi/asm-generic/errno-base.h:#define    ENODEV        
>> 19    /* No such device */
>>
>> this is returned by in `drivers/acpi/cppc_acpi.c`:
>>
>> ```
>> /**
>>   * cppc_get_perf_caps - Get a CPU's performance capabilities.
>>   * @cpunum: CPU from which to get capabilities info.
>>   * @perf_caps: ptr to cppc_perf_caps. See cppc_acpi.h
>>   *
>>   * Return: 0 for success with perf_caps populated else -ERRNO.
>>   */
>> int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
>> {
>>          struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
>>          […]
>>          if (!cpc_desc) {
>>                  pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
>>                  return -ENODEV;
>>          }
>>          […]
>> }
>> ```
> 
> @AMD folks, just for clarity. Did Dell something with their firmware? If 
> so, are you going to work with Dell on a solution, or do I need to 
> report the issue to them?
> 

I feel if there is a BIOS bug in hardware you purchased, you should 
report a bug to the hardware creator for them to fix.