linux-kernel - Re: [PATCH v9 20/31] x86/resctrl: Find and enable usable telemetry events

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Message-ID: <8748a2ab-f25f-462e-b769-9afbe0462996@intel.com>
Date: Tue, 9 Sep 2025 20:40:22 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>, Ilpo Järvinen
	<ilpo.jarvinen@...ux.intel.com>
CC: Fenghua Yu <fenghuay@...dia.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>, Chen Yu
	<yu.c.chen@...el.com>, <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v9 20/31] x86/resctrl: Find and enable usable telemetry
 events

Hi Tony,

On 9/3/25 11:19 AM, Luck, Tony wrote:

> 
> Updated patch with changes applied below. Also pushed to
> git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux.git rdt-aet-v10-wip
> 
> -Tony
> 
> From 19f90ec0c526791be589fe3ff4797536f7e9e9c9 Mon Sep 17 00:00:00 2001
> From: Tony Luck <tony.luck@...el.com>
> Date: Mon, 25 Aug 2025 10:47:06 -0700
> Subject: [PATCH 20/31] x86/resctrl: Find and enable usable telemetry events
> 
> The INTEL_PMT driver provides telemetry region structures of the

"INTEL_PMT" -> "INTEL_PMT_TELEMETRY"

> types requested by resctrl.
> 
> Scan these structures to discover which pass sanity checks:
> 
> 1) They have guid known to resctrl.
> 2) They have a valid package ID.
> 3) The enumerated size of the MMIO region matches the expected
>    value from the XML description file.
> 4) At least one region passes the above checks.

Above describes how resctrl determines "valid" telemetry regions.

> 
> Enable the active events in resctrl filesystem to make them available to

This jumps from "valid telemetry regions" to "active events" without a
connection between the two.


> user space. Pass a pointer to the pmt_event structure of the event within
> the struct event_group that resctrl stores in mon_evt::arch_priv. resctrl
> passes this pointer back when asking to read the event data which enables
> the data to be found in MMIO.
> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---
>  arch/x86/kernel/cpu/resctrl/intel_aet.c | 38 +++++++++++++++++++++++--
>  1 file changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
> index 93862060652a..e36b3790733b 100644
> --- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
> +++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
> @@ -20,9 +20,11 @@
>  #include <linux/intel_pmt_features.h>
>  #include <linux/intel_vsec.h>
>  #include <linux/overflow.h>
> +#include <linux/printk.h>
>  #include <linux/resctrl.h>
>  #include <linux/resctrl_types.h>
>  #include <linux/stddef.h>
> +#include <linux/topology.h>
>  #include <linux/types.h>
>  
>  #include "internal.h"
> @@ -111,12 +113,44 @@ static struct event_group *known_perf_event_groups[] = {
>  	for (_peg = (_grp); _peg < &_grp[ARRAY_SIZE(_grp)]; _peg++)	\
>  		if ((*_peg)->pfg)
>  
> -/* Stub for now */
> -static bool enable_events(struct event_group *e, struct pmt_feature_group *p)
> +static bool skip_telem_region(struct telemetry_region *tr, struct event_group *e)
>  {
> +	if (tr->guid != e->guid)
> +		return true;
> +	if (tr->plat_info.package_id >= topology_max_packages()) {
> +		pr_warn("Bad package %d in guid 0x%x\n", tr->plat_info.package_id,

%d -> %u?

> +			tr->guid);
> +		return true;
> +	}
> +	if (tr->size != e->mmio_size) {
> +		pr_warn("MMIO space wrong size (%zu bytes) for guid 0x%x. Expected %zu bytes.\n",
> +			tr->size, e->guid, e->mmio_size);
> +		return true;
> +	}
> +
>  	return false;
>  }
>  

Reinette