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)

[Paul Menzel <pmenzel@molgen.mpg.de>]

[Cc: +x86 maintainers and ACPI list]

Dear Linux folks,


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;
         }
         […]
}
```

Just for your information.


Kind regards,

Paul


> PS:
> 
>> -- 
>>
>> Thanks and Regards
>>
>> Gautham.
> 
> Only if you care: Your signature delimiter misses a space at the end [2].
> 
> 
> [1]: https://www.dell.com/support/manuals/de-de/poweredge-r7625/per7625_ism_pub/system-profile-settings?guid=guid-9f6b6652-4079-45e7-90f5-1c8feee08ec0&lang=en-us
> [2]: https://en.wikipedia.org/wiki/Signature_block#Standard_delimiter
[3]: 
https://lore.kernel.org/linux-pm/d09f52d8-e084-4875-9608-5b3db2554f3d@molgen.mpg.de/T/#t