linux-kernel - Re: [PATCH v8 13/32] x86,fs/resctrl: Handle events that can be read from any CPU

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Message-ID: <28b4983f-76ce-4fb4-8943-ef98d2c2fb52@intel.com>
Date: Wed, 13 Aug 2025 21:12:03 -0700
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 v8 13/32] x86,fs/resctrl: Handle events that can be read
 from any CPU

Hi Tony,

On 8/11/25 11:16 AM, Tony Luck wrote:

...

> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index c3f697da612b..d6585f7d1c9e 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -356,15 +356,47 @@ static struct mbm_state *get_mbm_state(struct rdt_l3_mon_domain *d, u32 closid,
>  	return state ? &state[idx] : NULL;
>  }
>  
> +/*
> + * Called from preemptible context via a direct call of mon_event_count() for
> + * events that can be read on any CPU.
> + * Called from preemptible but non-migratable process context (mon_event_count()
> + * via smp_call_on_cpu()) OR non-preemptible context (mon_event_count() via
> + * smp_call_function_any()) for events that need to be read on a specific CPU.
> + */
> +static bool cpu_on_correct_domain(struct rmid_read *rr)

Function returns bool ...

> +{
> +	struct cacheinfo *ci;
> +	int cpu;
> +
> +	/* Any CPU is OK for this event */
> +	if (rr->evt->any_cpu)
> +		return true;
> +
> +	cpu = smp_processor_id();
> +
> +	/* Single domain. Must be on a CPU in that domain. */
> +	if (rr->hdr)
> +		return cpumask_test_cpu(cpu, &rr->hdr->cpu_mask);
> +
> +	if (WARN_ON_ONCE(rr->r->rid != RDT_RESOURCE_L3))
> +		return -EINVAL;

return false?

> +
> +	/* Summing domains that share a cache, must be on a CPU for that cache. */
> +	ci = get_cpu_cacheinfo_level(cpu, RESCTRL_L3_CACHE);
> +
> +	return ci && ci->id == rr->ci_id;
> +}
> +
Reinette