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 10:16:08 -0500
From:   "Moger, Babu" <babu.moger@....com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.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, 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 4/19/23 08:20, Ilpo Järvinen wrote:
> 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.

Yes. It is because of this check.
    if (rft->fflags && ((fflags & rft->fflags) == rft->fflags)) {

I am not sure about "== rft->fflags" check. If I remove this check then I
may not have to do all this trick. I can try that.


> 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?

Yes. Let me experiment little bit.
Thanks
Babu
> 
>> +			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.
> 

-- 
Thanks
Babu Moger