linux-kernel - Re: [PATCH v6 10/42] x86/resctrl: Remove rdtgroup from update_cpu_closid

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Message-ID: <08d74c2f-29d8-4fd4-8f03-48c093ef7b61@amd.com>
Date: Thu, 27 Feb 2025 14:25:09 -0600
From: "Moger, Babu" <babu.moger@....com>
To: James Morse <james.morse@....com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Cc: Reinette Chatre <reinette.chatre@...el.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, H Peter Anvin <hpa@...or.com>,
 shameerali.kolothum.thodi@...wei.com,
 D Scott Phillips OS <scott@...amperecomputing.com>,
 carl@...amperecomputing.com, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>,
 Shanker Donthineni <sdonthineni@...dia.com>,
 Shaopeng Tan <tan.shaopeng@...fujitsu.com>, Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v6 10/42] x86/resctrl: Remove rdtgroup from
 update_cpu_closid_rmid()

Hi James,

On 2/7/25 12:17, James Morse wrote:
> update_cpu_closid_rmid() takes a struct rdtgroup as an argument, which
> it uses to update the local CPUs default pqr values. This is a problem
> once the resctrl parts move out to /fs/, as the arch code cannot
> poke around inside struct rdtgroup.
> 
> Rename update_cpu_closid_rmid() as resctrl_arch_sync_cpus_defaults()
> to be used as the target of an IPI, and pass the effective CLOSID
> and RMID in a new struct.
> 
> Co-developed-by: Dave Martin <Dave.Martin@....com>
> Signed-off-by: Dave Martin <Dave.Martin@....com>
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: Carl Worth <carl@...amperecomputing.com> # arm64
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> ---
> Changes since v1:
>  * To clarify the meanings of the new helper and struct:
> 
>    Rename resctrl_arch_sync_cpu_default() to
>    resctrl_arch_sync_cpu_closid_rmid();
> 
>    Rename struct resctrl_cpu_sync to struct resctrl_cpu_defaults;
> 
>    Flesh out the comment block in <linux/resctrl.h>.
> 
>    No functional change.
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 17 +++++++++++++----
>  include/linux/resctrl.h                | 22 ++++++++++++++++++++++
>  2 files changed, 35 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index f706e5a288b1..62d9a50c7bba 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -355,13 +355,13 @@ static int rdtgroup_cpus_show(struct kernfs_open_file *of,
>   * from update_closid_rmid() is protected against __switch_to() because
>   * preemption is disabled.
>   */
> -static void update_cpu_closid_rmid(void *info)
> +void resctrl_arch_sync_cpu_closid_rmid(void *info)
>  {
> -	struct rdtgroup *r = info;
> +	struct resctrl_cpu_defaults *r = info;
>  
>  	if (r) {
>  		this_cpu_write(pqr_state.default_closid, r->closid);
> -		this_cpu_write(pqr_state.default_rmid, r->mon.rmid);
> +		this_cpu_write(pqr_state.default_rmid, r->rmid);
>  	}
>  
>  	/*
> @@ -376,11 +376,20 @@ static void update_cpu_closid_rmid(void *info)
>   * Update the PGR_ASSOC MSR on all cpus in @cpu_mask,
>   *
>   * Per task closids/rmids must have been set up before calling this function.
> + * @r may be NULL.
>   */
>  static void
>  update_closid_rmid(const struct cpumask *cpu_mask, struct rdtgroup *r)
>  {
> -	on_each_cpu_mask(cpu_mask, update_cpu_closid_rmid, r, 1);
> +	struct resctrl_cpu_defaults defaults, *p = NULL;
> +
> +	if (r) {
> +		defaults.closid = r->closid;
> +		defaults.rmid = r->mon.rmid;
> +		p = &defaults;
> +	}
> +
> +	on_each_cpu_mask(cpu_mask, resctrl_arch_sync_cpu_closid_rmid, p, 1);
>  }
>  
>  static int cpus_mon_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index a939c0cec7fe..da3b344d06d3 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -266,6 +266,28 @@ struct resctrl_schema {
>  	u32				num_closid;
>  };
>  
> +struct resctrl_cpu_defaults {
> +	u32 closid;
> +	u32 rmid;
> +};
> +

Can you please explain why this is part of resctrl.h?

Isn't this part of architecture specific definition?

> +/**
> + * resctrl_arch_sync_cpu_closid_rmid() - Refresh this CPU's CLOSID and RMID.
> + *					 Call via IPI.
> + * @info:	If non-NULL, a pointer to a struct resctrl_cpu_defaults
> + *		specifying the new CLOSID and RMID for tasks in the default
> + *		resctrl ctrl and mon group when running on this CPU.  If NULL,
> + *		this CPU is not re-assigned to a different default group.
> + *
> + * Propagates reassignment of CPUs and/or tasks to different resctrl groups
> + * when requested by the resctrl core code.
> + *
> + * This function records the per-cpu defaults specified by @info (if any),
> + * and then reconfigures the CPU's hardware CLOSID and RMID for subsequent
> + * execution based on @current, in the same way as during a task switch.
> + */
> +void resctrl_arch_sync_cpu_closid_rmid(void *info);
> +
>  /**
>   * resctrl_get_default_ctrl() - Return the default control value for this
>   *                              resource.

-- 
Thanks
Babu Moger