linux-kernel - Re: [PATCH v6 17/30] x86/resctrl: Discover hardware telemetry events

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Message-ID: <aF7dt2iQpvuahZil@agluck-desk3>
Date: Fri, 27 Jun 2025 11:06:47 -0700
From: "Luck, Tony" <tony.luck@...el.com>
To: Fenghua Yu <fenghuay@...dia.com>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
	Peter Newman <peternewman@...gle.com>,
	James Morse <james.morse@....com>, Babu Moger <babu.moger@....com>,
	Drew Fustini <dfustini@...libre.com>,
	Dave Martin <Dave.Martin@....com>,
	Anil Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	Chen Yu <yu.c.chen@...el.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH v6 17/30] x86/resctrl: Discover hardware telemetry events

On Thu, Jun 26, 2025 at 09:49:26AM -0700, Tony Luck wrote:
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 71019b3b54ea..8eb68d2230be 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -512,6 +512,9 @@ config X86_CPU_RESCTRL
>  	select ARCH_HAS_CPU_RESCTRL
>  	select RESCTRL_FS
>  	select RESCTRL_FS_PSEUDO_LOCK
> +	select X86_PLATFORM_DEVICES
> +	select INTEL_VSEC
> +	select INTEL_PMT_TELEMETRY
>  	help
>  	  Enable x86 CPU resource control support.
>  

The list of dependencies to "select" keeps growing. "lkp"
just told me that "INTEL_VSEC" depends on "PCI".

An alternative approach is to just add:

	depends on INTEL_PMT_DISCOVERY=y

instead of all the extra "select" lines.

Pro: This describes exactly what is needed. The INTEL_PMT_DISCOVERY
driver must be built-in to the kernel so that resctrl can enumerate the
telemetry features.

Con: "make olddefconfig" will now drop X86_CPU_RESCTRL until the user
hunts down and enables the chain of dependencies to get RESCTRL turned
back on again.

-Tony