linux-kernel - Re: [PATCH v7 23/31] x86/resctrl: Handle domain creation/deletion for RDT_RESOURCE_PERF

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Message-ID: <45d69983-c4fe-494b-a43c-7686db36be76@intel.com>
Date: Fri, 25 Jul 2025 16:46:00 -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 v7 23/31] x86/resctrl: Handle domain creation/deletion for
 RDT_RESOURCE_PERF_PKG

Hi Tony,

On 7/11/25 4:53 PM, Tony Luck wrote:
> The L3 resource has several requirements for domains. There are structures
> that hold the 64-bit values of counters, and elements to keep track of
> the overflow and limbo threads.
> 
> None of these are needed for the PERF_PKG resource. The hardware counters
> are wide enough that they do not wrap around for decades.
> 
> Define a new rdt_perf_pkg_mon_domain structure which just consists of
> the standard rdt_domain_hdr to keep track of domain id and CPU mask.

This patch does more than this. 

> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---
>  arch/x86/kernel/cpu/resctrl/core.c | 41 ++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 63baab53821a..c954171073c7 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -547,6 +547,38 @@ static void l3_mon_domain_setup(int cpu, int id, struct rdt_resource *r, struct
>  	}
>  }
>  
> +/**
> + * struct rdt_perf_pkg_mon_domain - CPUs sharing an Intel-PMT-scoped resctrl monitor resource

What does "Intel-PMT-scoped" mean?

> + * @hdr:	common header for different domain types
> + */
> +struct rdt_perf_pkg_mon_domain {
> +	struct rdt_domain_hdr   hdr;
> +};
> +
> +static void setup_intel_aet_mon_domain(int cpu, int id, struct rdt_resource *r,
> +				       struct list_head *add_pos)

This belongs in arch/x86/kernel/cpu/resctrl/intel_aet.c?

> +{
> +	struct rdt_perf_pkg_mon_domain *d;
> +	int err;
> +
> +	d = kzalloc_node(sizeof(*d), GFP_KERNEL, cpu_to_node(cpu));
> +	if (!d)
> +		return;
> +
> +	d->hdr.id = id;
> +	d->hdr.type = RESCTRL_MON_DOMAIN;
> +	d->hdr.rid = r->rid;
> +	cpumask_set_cpu(cpu, &d->hdr.cpu_mask);
> +	list_add_tail_rcu(&d->hdr.list, add_pos);
> +
> +	err = resctrl_online_mon_domain(r, &d->hdr);
> +	if (err) {
> +		list_del_rcu(&d->hdr.list);
> +		synchronize_rcu();
> +		kfree(d);
> +	}
> +}
> +
>  static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
>  {
>  	int id = get_domain_id_from_scope(cpu, r->mon_scope);
> @@ -574,6 +606,9 @@ static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
>  	case RDT_RESOURCE_L3:
>  		l3_mon_domain_setup(cpu, id, r, add_pos);
>  		break;
> +	case RDT_RESOURCE_PERF_PKG:
> +		setup_intel_aet_mon_domain(cpu, id, r, add_pos);
> +		break;
>  	default:
>  		WARN_ON_ONCE(1);
>  	}
> @@ -670,6 +705,12 @@ static void domain_remove_cpu_mon(int cpu, struct rdt_resource *r)
>  		synchronize_rcu();
>  		l3_mon_domain_free(hw_dom);
>  		break;
> +	case RDT_RESOURCE_PERF_PKG:
> +		resctrl_offline_mon_domain(r, hdr);
> +		list_del_rcu(&hdr->list);
> +		synchronize_rcu();
> +		kfree(container_of(hdr, struct rdt_perf_pkg_mon_domain, hdr));
> +		break;
>  	default:
>  		pr_warn_once("Unknown resource rid=%d\n", r->rid);
>  		break;

Reinette