linux-kernel - Re: [PATCH v4 05/31] fs/resctrl: Set up Kconfig options for telemetry events

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Message-ID: <621ff36f-eaa7-4dba-909a-e50977abf6dc@intel.com>
Date: Sat, 10 May 2025 17:58:36 +0800
From: "Chen, Yu C" <yu.c.chen@...el.com>
To: Tony Luck <tony.luck@...el.com>
CC: <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<patches@...ts.linux.dev>, Peter Newman <peternewman@...gle.com>, James Morse
	<james.morse@....com>, Dave Martin <Dave.Martin@....com>, Babu Moger
	<babu.moger@....com>, Anil Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	Drew Fustini <dfustini@...libre.com>, Fenghua Yu <fenghuay@...dia.com>,
	Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>, Reinette Chatre
	<reinette.chatre@...el.com>
Subject: Re: [PATCH v4 05/31] fs/resctrl: Set up Kconfig options for telemetry
 events

Hi Tony,

On 4/29/2025 8:33 AM, Tony Luck wrote:
> Intel RMID based telemetry events are counted by each CPU core
> and then aggregated by one or more per-socket micro controllers.
> Enumeration support is provided by the Intel PMT subsystem.
> 
> N.B. Patches for the Intel PMT system are still in progress.
> They will define an INTEL_PMT_DISCOVERY Kconfig symbol that
> will be one of the dependencies. This is commented out for
> now. Final version will include this dependency.
> 
> arch/x86 selects this option based on:
> 
> X86_64: Counter registers are in MMIO space. There is no readq()
> function on 32-bit. Emulation is possible with readl(), but there
> are races. Running 32-bit kernels on systems that support this
> feature seems pointless.
> 
> CPU_SUP_INTEL: It is an Intel specific feature.
> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---
>   arch/x86/Kconfig                       | 1 +
>   drivers/platform/x86/intel/pmt/Kconfig | 7 +++++++
>   2 files changed, 8 insertions(+)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 5a09acf41c8e..19107fdb4264 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -508,6 +508,7 @@ config X86_CPU_RESCTRL
>   	bool "x86 CPU resource control support"
>   	depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
>   	depends on MISC_FILESYSTEMS
> +	select INTEL_AET_RESCTRL if (X86_64 && CPU_SUP_INTEL)

Not sure if if it is expected, I got the following warning
during compiling:
WARNING: unmet direct dependencies detected for INTEL_AET_RESCTRL
   Depends on [n]: X86_PLATFORM_DEVICES [=y] && INTEL_PMT_TELEMETRY [=n]
   Selected by [y]:
   - X86_CPU_RESCTRL [=y] && X86 [=y] && (CPU_SUP_INTEL [=y] || 
CPU_SUP_AMD [=y]) && MISC_FILESYSTEMS [=y] && X86_64 [=y] && 
CPU_SUP_INTEL [=y]

I think this is because the INTEL_PMT_TELEMETRY is disabled.
Does it make sense to add the dependency of INTEL_PMT_TELEMETRY
to auto-select for INTEL_AET_RESCTRL?

select INTEL_AET_RESCTRL if (X86_64 && CPU_SUP_INTEL && INTEL_PMT_TELEMETRY)

thanks，
Chenyu

>   	select ARCH_HAS_CPU_RESCTRL
>   	select RESCTRL_FS
>   	select RESCTRL_FS_PSEUDO_LOCK
> diff --git a/drivers/platform/x86/intel/pmt/Kconfig b/drivers/platform/x86/intel/pmt/Kconfig
> index e916fc966221..3a8ce39d1004 100644
> --- a/drivers/platform/x86/intel/pmt/Kconfig
> +++ b/drivers/platform/x86/intel/pmt/Kconfig
> @@ -38,3 +38,10 @@ config INTEL_PMT_CRASHLOG
>   
>   	  To compile this driver as a module, choose M here: the module
>   	  will be called intel_pmt_crashlog.
> +
> +config INTEL_AET_RESCTRL
> +	depends on INTEL_PMT_TELEMETRY # && INTEL_PMT_DISCOVERY
> +	bool
> +	help
> +	  Architecture config should "select" this option to enable
> +	  support for RMID telemetry events in the resctrl file system.