linux-kernel - Re: [PATCH v4 7/7] x86/resctrl: Add debug files when mounted with debug option

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Date:   Wed, 19 Apr 2023 16:20:50 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Babu Moger <babu.moger@....com>
cc:     corbet@....net, Reinette Chatre <reinette.chatre@...el.com>,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        fenghua.yu@...el.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, paulmck@...nel.org, akpm@...ux-foundation.org,
        quic_neeraju@...cinc.com, rdunlap@...radead.org,
        damien.lemoal@...nsource.wdc.com, songmuchun@...edance.com,
        peterz@...radead.org, jpoimboe@...nel.org, pbonzini@...hat.com,
        chang.seok.bae@...el.com, pawan.kumar.gupta@...ux.intel.com,
        jmattson@...gle.com, daniel.sneddon@...ux.intel.com,
        sandipan.das@....com, tony.luck@...el.com, james.morse@....com,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        bagasdotme@...il.com, eranian@...gle.com,
        christophe.leroy@...roup.eu, pawan.kumar.gupta@...ux.intel.com,
        jarkko@...nel.org, adrian.hunter@...el.com, quic_jiles@...cinc.com,
        peternewman@...gle.com
Subject: Re: [PATCH v4 7/7] x86/resctrl: Add debug files when mounted with
 debug option

On Mon, 17 Apr 2023, Babu Moger wrote:

> Add the debug files to the resctrl hierarchy.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
>  arch/x86/kernel/cpu/resctrl/internal.h |    1 +
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |   54 +++++++++++++++++++++++++++++++-
>  2 files changed, 54 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 1eac07ebc31b..855109abb480 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -288,6 +288,7 @@ struct rdtgroup {
>  #define RFTYPE_TOP			BIT(4)
>  #define RFTYPE_RES_CACHE		BIT(5)
>  #define RFTYPE_RES_MB			BIT(6)
> +#define RFTYPE_DEBUG			BIT(7)
>  #define RFTYPE_CTRL_INFO		(RFTYPE_INFO | RFTYPE_CTRL)
>  #define RFTYPE_MON_INFO			(RFTYPE_INFO | RFTYPE_MON)
>  #define RFTYPE_TOP_INFO			(RFTYPE_INFO | RFTYPE_TOP)
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 15ded0dd5b09..1ec4359348c2 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1880,6 +1880,7 @@ static struct rftype res_common_files[] = {
>  		.mode		= 0444,
>  		.kf_ops		= &rdtgroup_kf_single_ops,
>  		.seq_show	= rdtgroup_rmid_show,
> +		.fflags		= RFTYPE_BASE | RFTYPE_DEBUG,
>  	},
>  	{
>  		.name		= "schemata",
> @@ -1909,6 +1910,7 @@ static struct rftype res_common_files[] = {
>  		.mode		= 0444,
>  		.kf_ops		= &rdtgroup_kf_single_ops,
>  		.seq_show	= rdtgroup_closid_show,
> +		.fflags		= RFTYPE_CTRL_BASE | RFTYPE_DEBUG,
>  	},
>  
>  };
> @@ -2420,6 +2422,49 @@ static int mkdir_mondata_all(struct kernfs_node *parent_kn,
>  			     struct rdtgroup *prgrp,
>  			     struct kernfs_node **mon_data_kn);
>  
> +static void resctrl_add_debug_files(void)
> +{
> +	struct rftype *rfts, *rft;
> +	int len;
> +
> +	rfts = res_common_files;
> +	len = ARRAY_SIZE(res_common_files);
> +
> +	lockdep_assert_held(&rdtgroup_mutex);
> +
> +	for (rft = rfts; rft < rfts + len; rft++) {
> +		if (rft->fflags & RFTYPE_DEBUG) {
> +			rft->fflags &= ~RFTYPE_DEBUG;

I don't fully follow why you need to play with ->fflags like this.

Is it for the ->fflags test in rdtgroup_add_files()? Can't you just do 
some extra masking there for RFTYPE_DEBUG based on resctrl_debug which 
you already keep?

> +			rdtgroup_add_file(rdtgroup_default.kn, rft);
> +		}
> +	}
> +
> +	kernfs_activate(rdtgroup_default.kn);
> +}
> +
> +static void resctrl_remove_debug_files(void)
> +{
> +	struct rftype *rfts, *rft;
> +	int len;
> +
> +	rfts = res_common_files;
> +	len = ARRAY_SIZE(res_common_files);
> +
> +	lockdep_assert_held(&rdtgroup_mutex);
> +
> +	for (rft = rfts; rft < rfts + len; rft++) {
> +		if (!strcmp(rft->name, "mon_hw_id")) {
> +			rft->fflags |= RFTYPE_DEBUG;
> +			kernfs_remove_by_name(rdtgroup_default.kn, rft->name);
> +		} else if (!strcmp(rft->name, "ctrl_hw_id")) {
> +			rft->fflags |= RFTYPE_DEBUG;
> +			kernfs_remove_by_name(rdtgroup_default.kn, rft->name);
> +		}
> +	}
> +
> +	kernfs_activate(rdtgroup_default.kn);
> +}
> +
>  static int rdt_enable_ctx(struct rdt_fs_context *ctx)
>  {
>  	int ret = 0;
> @@ -2433,8 +2478,10 @@ static int rdt_enable_ctx(struct rdt_fs_context *ctx)
>  	if (!ret && ctx->enable_mba_mbps)
>  		ret = set_mba_sc(true);
>  
> -	if (!ret && ctx->enable_debug)
> +	if (!ret && ctx->enable_debug) {
>  		resctrl_debug = true;
> +		resctrl_add_debug_files();
> +	}
>  
>  	return ret;
>  }
> @@ -2851,6 +2898,11 @@ static void rdt_kill_sb(struct super_block *sb)
>  
>  	set_mba_sc(false);
>  
> +	if (resctrl_debug) {
> +		resctrl_remove_debug_files();
> +		resctrl_debug = false;

Logically, this false assignment belongs to the earlier patch.

-- 
 i.