linux-kernel - Re: [PATCH v13 11/32] x86,fs/resctrl: Handle events that can be read from any CPU

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: <49aaa6fc-b75e-4394-9abd-07a6b4a0822c@intel.com>
Date: Wed, 12 Nov 2025 20:02:24 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>, 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>
CC: <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v13 11/32] x86,fs/resctrl: Handle events that can be read
 from any CPU

Hi Tony,

On 10/29/25 9:20 AM, Tony Luck wrote:
> resctrl assumes that monitor events can only be read from a CPU in the
> cpumask_t set of each domain.  This is true for x86 events accessed
> with an MSR interface, but may not be true for other access methods such
> as MMIO.
> 
> Introduce and use flag mon_evt::any_cpu, settable by architecture, that
> indicates there are no restrictions on which CPU can read that event.
> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---

This implies a generic change while __l3_mon_event_count() cannot support it.
While I understand why cpu_on_correct_domain() was removed, the existing checking
requires DEBUG_PREEMPT to be set so I think it would be helpful if there is something
like a WARN_ON_ONCE(rr->evt->any_cpu) before calling __l3_mon_event_count() to help
catch issues.

Reinette