linux-kernel - Re: [PATCH 2/2 v3] intel_pstate: add kernel parameter to enable loading on Sun X86 servers.

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Date:	Wed, 26 Nov 2014 08:08:35 +0800
From:	ethan <ethan.kernel@...il.com>
To:	Dirk Brandewie <dirk.brandewie@...il.com>
Cc:	Ethan Zhao <ethan.zhao@...cle.com>,
	"linda.knippers@...com" <linda.knippers@...com>,
	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"corbet@....net" <corbet@....net>,
	"dirk.j.brandewie@...el.com" <dirk.j.brandewie@...el.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2 v3] intel_pstate: add kernel parameter to enable loading on  Sun X86 servers.

Dirk,

> 在 2014年11月25日，22:51，Dirk Brandewie <dirk.brandewie@...il.com> 写道：
> 
>> On 11/24/2014 08:59 PM, Ethan Zhao wrote:
>> To force loading on Oracle Sun X86 servers, provide one kernel command line
>> parameter
>> 
>>   intel_pstate = onora
>> 
>> For those who be aware of the risk doing so.
>> 
>> Signed-off-by: Ethan Zhao <ethan.zhao@...cle.com>
>> ---
>>  v2: change to hardware vendor specific naming parameter.
>> 
>>  Documentation/kernel-parameters.txt | 3 +++
>>  drivers/cpufreq/intel_pstate.c      | 6 +++++-
>>  2 files changed, 8 insertions(+), 1 deletion(-)
>> 
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index 479f332..e4b1b81 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -1446,6 +1446,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>>                 disable
>>                   Do not enable intel_pstate as the default
>>                   scaling driver for the supported processors
>> +               onora
>> +                 Enable loading intel_pstate on Oracle Sun Servers(X86).
>> +             only for those who be aware of the risk.
> 
> What are the risks?  What is the behaviour if platform power management is
> enabled and intel_pstate is trying to control P state selection as well?
So far test shows intel_pstate could run.
> 
> If intel_pstate will be able to successfully control P state selection
> with platform power management enabled then how about the name "oracle_force"?
Oracle_force seems a suggestion from oracle, not an option would be used as choice
In case of no other method.

> Also the documentation should say what the risks are.

The risk is the sever lost power capping capability, that may cause service down, for example,
The server has two power supply units, one is faulty, without power capping, could't limit the power consumption within one power supply's capability, this could cause the last power supply
Unit overload and power down.

Thanks,
Ethan
> 
>> 
>>      intremap=    [X86-64, Intel-IOMMU]
>>              on    enable Interrupt Remapping (default)
>> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
>> index fa67fb3..e49b050 100644
>> --- a/drivers/cpufreq/intel_pstate.c
>> +++ b/drivers/cpufreq/intel_pstate.c
>> @@ -866,6 +866,7 @@ static struct cpufreq_driver intel_pstate_driver = {
>>  };
>> 
>>  static int __initdata no_load;
>> +static unsigned int  load_on_sun;
>> 
>>  static int intel_pstate_msrs_not_valid(void)
>>  {
>> @@ -1005,7 +1006,8 @@ static bool intel_pstate_platform_pwr_mgmt_exists(void)
>>          if (!strncmp(hdr.oem_id, v_info->oem_id, ACPI_OEM_ID_SIZE) &&
>>              !strncmp(hdr.oem_table_id, v_info->oem_table_id,
>>                  ACPI_OEM_TABLE_ID_SIZE) &&
>> -            intel_pstate_has_acpi_ppc())
>> +            intel_pstate_has_acpi_ppc() &&
>> +            !load_on_sun)
>>              return true;
>>      }
>> 
>> @@ -1080,6 +1082,8 @@ static int __init intel_pstate_setup(char *str)
>> 
>>      if (!strcmp(str, "disable"))
>>          no_load = 1;
>> +    if (!strcmp(str, "onora"))
>> +        load_on_sun = 1;
>>      return 0;
>>  }
>>  early_param("intel_pstate", intel_pstate_setup);
> 
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