linux-kernel - Re: [PATCH v8 09/32] x86,fs/resctrl: Use struct rdt_domain_hdr instead of struct rdt_mon

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Message-ID: <626be12b-1bd9-4e7d-86e9-596e5c02a039@intel.com>
Date: Wed, 13 Aug 2025 21:06:54 -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>, Anil Keshavamurthy <anil.s.keshavamurthy@...el.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 09/32] x86,fs/resctrl: Use struct rdt_domain_hdr
 instead of struct rdt_mon_domain

Hi Tony,

On 8/11/25 11:16 AM, Tony Luck wrote:
> All monitoring events are associated with the L3 resource and it made
> sense to use the L3 specific "struct rdt_mon_domain *" arguments to
> functions manipulating domains.
> 
> But the addition of monitor events tied to other resources changes
> this assumption.

What assumption?

How about:

"Telemetry events will be tied to another resource. This requires the
 functions that manipulate domains to not be L3 specific."

> 
> Change the calling sequence to use the generic struct rdt_domain_hdr for
> domain addition and deletion to preserve as much common code as possible.
> This will simplify enabling of enumeration of domains for events in
> other resources.
> 
> Make the same change to allow reading events in other resources. In
> this case the code flow passes from mon_event_read() via smp_call*()
> eventually to __mon_event_count() so the rmid_read::d field is replaced

"so the rmid_read::d field is replaced" -> "so replace the L3 specific domain
pointer rmid_read::d with rmid_read::hdr that points to the generic domain
header"
(switch to imperative and remove unnecessary "field" term)

> with the new rmid_read::hdr field.
> 
> The mon_data structure is unchanged, but documentation is updated
> to note that mon_data::sum is only used for RDT_RESOURCE_L3.

wait ... this looks familiar ... (looks at v7 feedback) ... same feedback
here as in v7 :(

> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---

...

> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 911100994fcd..7fd6cd7348fb 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -529,7 +529,7 @@ static void l3_mon_domain_setup(int cpu, int id, struct rdt_resource *r, struct
>  
>  	list_add_tail_rcu(&d->hdr.list, add_pos);
>  
> -	err = resctrl_online_mon_domain(r, d);
> +	err = resctrl_online_mon_domain(r, &d->hdr);
>  	if (err) {
>  		list_del_rcu(&d->hdr.list);
>  		synchronize_rcu();
> @@ -611,7 +611,7 @@ static void domain_remove_cpu_ctrl(int cpu, struct rdt_resource *r)
>  	hw_dom = resctrl_to_arch_ctrl_dom(d);
>  
>  	resctrl_offline_ctrl_domain(r, d);
> -	list_del_rcu(&d->hdr.list);
> +	list_del_rcu(&hdr->list);
>  	synchronize_rcu();
>  

Looks like the change intended for patch #8 landed here instead.

>  	/*


Reinette