linux-kernel - Re: [PATCH v7 03/24] x86/resctrl: Create helper for RMID allocation and mondata dir creation

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Date:   Thu, 9 Nov 2023 14:28:55 -0600
From:   "Moger, Babu" <babu.moger@....com>
To:     James Morse <james.morse@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        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,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v7 03/24] x86/resctrl: Create helper for RMID allocation
 and mondata dir creation

Hi James,

On 10/25/23 13:03, James Morse wrote:
> When monitoring is supported, each monitor and control group is allocated
> an RMID. For control groups, rdtgroup_mkdir_ctrl_mon() later goes on to
> allocate the CLOSID.
> 
> MPAM's equivalent of RMID are not an independent number, so can't be
> allocated until the CLOSID is known. An RMID allocation for one CLOSID
> may fail, whereas another may succeed depending on how many monitor
> groups a control group has.
> 
> The RMID allocation needs to move to be after the CLOSID has been
> allocated.
> 
> Move the RMID allocation and mondata dir creation to a helper, this
> makes a subsequent change easier to read.
> 
> Tested-by: Peter Newman <peternewman@...gle.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: James Morse <james.morse@....com>

Reviewed-by: Babu Moger <babu.moger@....com>

> ---
> Changes since v4:
>  * Fixed typo in commit message, moved some words around.
> 
> No changes since v6
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 42 +++++++++++++++++---------
>  1 file changed, 27 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 69a1de92384a..1eb3a3075093 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -3293,6 +3293,30 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
>  	return ret;
>  }
>  
> +static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
> +{
> +	int ret;
> +
> +	if (!rdt_mon_capable)
> +		return 0;
> +
> +	ret = alloc_rmid();
> +	if (ret < 0) {
> +		rdt_last_cmd_puts("Out of RMIDs\n");
> +		return ret;
> +	}
> +	rdtgrp->mon.rmid = ret;
> +
> +	ret = mkdir_mondata_all(rdtgrp->kn, rdtgrp, &rdtgrp->mon.mon_data_kn);
> +	if (ret) {
> +		rdt_last_cmd_puts("kernfs subdir error\n");
> +		free_rmid(rdtgrp->mon.rmid);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
>  			     const char *name, umode_t mode,
>  			     enum rdt_group_type rtype, struct rdtgroup **r)
> @@ -3365,20 +3389,10 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
>  		goto out_destroy;
>  	}
>  
> -	if (rdt_mon_capable) {
> -		ret = alloc_rmid();
> -		if (ret < 0) {
> -			rdt_last_cmd_puts("Out of RMIDs\n");
> -			goto out_destroy;
> -		}
> -		rdtgrp->mon.rmid = ret;
> +	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
> +	if (ret)
> +		goto out_destroy;
>  
> -		ret = mkdir_mondata_all(kn, rdtgrp, &rdtgrp->mon.mon_data_kn);
> -		if (ret) {
> -			rdt_last_cmd_puts("kernfs subdir error\n");
> -			goto out_idfree;
> -		}
> -	}
>  	kernfs_activate(kn);
>  
>  	/*
> @@ -3386,8 +3400,6 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
>  	 */
>  	return 0;
>  
> -out_idfree:
> -	free_rmid(rdtgrp->mon.rmid);
>  out_destroy:
>  	kernfs_put(rdtgrp->kn);
>  	kernfs_remove(rdtgrp->kn);

-- 
Thanks
Babu Moger