linux-kernel - Re: [PATCH v17 19/32] x86/resctrl: Find and enable usable telemetry events

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Message-ID: <20260109121616.GBaWDxkGvgJ6sd133q@fat_crate.local>
Date: Fri, 9 Jan 2026 13:16:16 +0100
From: Borislav Petkov <bp@...en8.de>
To: Tony Luck <tony.luck@...el.com>
Cc: 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>, Chen Yu <yu.c.chen@...el.com>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev
Subject: Re: [PATCH v17 19/32] x86/resctrl: Find and enable usable telemetry
 events

On Wed, Dec 17, 2025 at 09:21:06AM -0800, Tony Luck wrote:
> -static bool enable_events(struct event_group *e, struct pmt_feature_group *p)
> +/*
> + * Clear the address field of regions that did not pass the checks in
> + * skip_telem_region() so they will not be used by intel_aet_read_event().
> + * This is safe to do because intel_pmt_get_regions_by_feature() allocates
> + * a new pmt_feature_group structure to return to each caller and only makes
> + * use of the pmt_feature_group::kref field when intel_pmt_put_feature_group()
> + * returns the structure.
> + */
> +static void mark_telem_region_unusable(struct telemetry_region *tr)
>  {
> +	tr->addr = NULL;
> +}

We probably don't really need such a silly helper which is used only once and,
AFAICT, doesn't grow any other functionality by the end of the patchset:

diff --git a/arch/x86/kernel/cpu/resctrl/intel_aet.c b/arch/x86/kernel/cpu/resctrl/intel_aet.c
index 4074fd43830e..7d0bd7b070a7 100644
--- a/arch/x86/kernel/cpu/resctrl/intel_aet.c
+++ b/arch/x86/kernel/cpu/resctrl/intel_aet.c
@@ -112,19 +112,6 @@ static struct event_group *known_event_groups[] = {
 	     _peg < &known_event_groups[ARRAY_SIZE(known_event_groups)];	\
 	     _peg++)
 
-/*
- * Clear the address field of regions that did not pass the checks in
- * skip_telem_region() so they will not be used by intel_aet_read_event().
- * This is safe to do because intel_pmt_get_regions_by_feature() allocates
- * a new pmt_feature_group structure to return to each caller and only makes
- * use of the pmt_feature_group::kref field when intel_pmt_put_feature_group()
- * returns the structure.
- */
-static void mark_telem_region_unusable(struct telemetry_region *tr)
-{
-	tr->addr = NULL;
-}
-
 static bool skip_telem_region(struct telemetry_region *tr, struct event_group *e)
 {
 	if (tr->guid != e->guid)
@@ -149,7 +136,16 @@ static bool group_has_usable_regions(struct event_group *e, struct pmt_feature_g
 
 	for (int i = 0; i < p->count; i++) {
 		if (skip_telem_region(&p->regions[i], e)) {
-			mark_telem_region_unusable(&p->regions[i]);
+			/*
+			 * Clear the address field of regions that did not pass the checks in
+			 * skip_telem_region() so they will not be used by intel_aet_read_event().
+			 * This is safe to do because intel_pmt_get_regions_by_feature() allocates
+			 * a new pmt_feature_group structure to return to each caller and only makes
+			 * use of the pmt_feature_group::kref field when intel_pmt_put_feature_group()
+			 * returns the structure.
+			 */
+			p->regions[i].addr = NULL;
+
 			continue;
 		}
 		usable_regions = true;


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette