linux-kernel - Re: [PATCH v3 03/19] x86/resctrl: Create helper for RMID allocation and mondata dir creation

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Date:   Tue, 21 Mar 2023 13:05:13 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     James Morse <james.morse@....com>
cc:     x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
        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>,
        Babu Moger <Babu.Moger@....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,
        xingxin.hx@...nanolis.org, baolin.wang@...ux.alibaba.com,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com
Subject: Re: [PATCH v3 03/19] x86/resctrl: Create helper for RMID allocation
 and mondata dir creation

On Mon, 20 Mar 2023, James Morse wrote:

> RMID are allocated for each monitor or control group directory, because
> each of these needs its own 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.
> 
> To make a subsequent change that does this easier to read, move the RMID
> allocation and mondata dir creation to a helper.
> 
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Signed-off-by: James Morse <james.morse@....com>
> ---
>  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 6ecaf34a4e32..b785beb0db26 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -3135,6 +3135,30 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
>  	return 0;
>  }
>  
> +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->closid, 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)
> @@ -3200,20 +3224,10 @@ 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);
>  
>  	/*
> @@ -3221,8 +3235,6 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
>  	 */
>  	return 0;
>  
> -out_idfree:
> -	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>  out_destroy:
>  	kernfs_put(rdtgrp->kn);
>  	kernfs_remove(rdtgrp->kn);
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>


-- 
 i.