linux-kernel - Re: [PATCH v6 18/30] x86/resctrl: Count valid telemetry aggregators per package

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aG6xGGiOy3xKL-t4@agluck-desk3>
Date: Wed, 9 Jul 2025 11:12:40 -0700
From: "Luck, Tony" <tony.luck@...el.com>
To: Reinette Chatre <reinette.chatre@...el.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>,
	Anil Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	Chen Yu <yu.c.chen@...el.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH v6 18/30] x86/resctrl: Count valid telemetry aggregators
 per package

On Tue, Jul 08, 2025 at 07:20:35PM -0700, Reinette Chatre wrote:
> As I understand there is 1:1 relationship between struct event_group and struct pmt_feature_group.
> It thus seems unnecessary to loop through all the telemetry regions of a struct pmt_feature_group
> if it is known to not be associated with the "event group"?
> Could it be helpful to add a new (hardcoded) event_group::id that is of type enum pmt_feature_id
> that can be used to ensure that only relevant struct pmt_feature_group is used to discover events
> for a particular struct event_group?
> 
> Another consideration is that this implementation seems to require that guids are unique across
> all telemetry regions of all RMID telemetry features, is this guaranteed?

The guids are unique. The XML file tags them like this:

	<TELEM:uniqueid>26557651</TELEM:uniqueid>

the "guid" naming of the value comes from the Intel PMT_DISCOVERY driver.

An alternative to adding the new event_group::id field would be to
separate the arrays of known event groups. I.e. change from:

static struct event_group *known_event_groups[] = {
        &energy_0x26696143,
        &perf_0x26557651,
};

to

static struct event_group *known_energy_event_groups[] = {
        &energy_0x26696143,
};

static struct event_group *known_perf_event_groups[] = {
        &perf_0x26557651,
};

then only scan the appropriate array that matches the
enum pmt_feature_id passed to get_pmt_feature().


With only one option in each array today this looks
like extra infrasctruture. But I already have a patch
for the next generation system that adds another guid.

-Tony