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

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Date:	Tue, 25 Nov 2014 06:51:35 -0800
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	Ethan Zhao <ethan.zhao@...cle.com>, linda.knippers@...com,
	viresh.kumar@...aro.org, rjw@...ysocki.net, corbet@....net
CC:	dirk.j.brandewie@...el.com, linux-doc@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	ethan.kernel@...il.com
Subject: Re: [PATCH 2/2 v3] intel_pstate: add kernel parameter to enable loading
 on  Sun X86 servers.

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?

If intel_pstate will be able to successfully control P state selection
with platform power management enabled then how about the name "oracle_force"?
Also the documentation should say what the risks are.

>
>   	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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