linux-kernel - Re: [RFC PATCH v3 11/17] x86/resctrl: Introduce mbm_total_cfg and mbm_local

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Date: Wed, 8 May 2024 10:57:33 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
 fenghua.yu@...el.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com
Cc: x86@...nel.org, hpa@...or.com, paulmck@...nel.org, rdunlap@...radead.org,
 tj@...nel.org, peterz@...radead.org, yanjiewtw@...il.com,
 kim.phillips@....com, lukas.bulwahn@...il.com, seanjc@...gle.com,
 jmattson@...gle.com, leitao@...ian.org, jpoimboe@...nel.org,
 rick.p.edgecombe@...el.com, kirill.shutemov@...ux.intel.com,
 jithu.joseph@...el.com, kai.huang@...el.com, kan.liang@...ux.intel.com,
 daniel.sneddon@...ux.intel.com, pbonzini@...hat.com, sandipan.das@....com,
 ilpo.jarvinen@...ux.intel.com, peternewman@...gle.com,
 maciej.wieczor-retman@...el.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, eranian@...gle.com, james.morse@....com
Subject: Re: [RFC PATCH v3 11/17] x86/resctrl: Introduce mbm_total_cfg and
 mbm_local_cfg

Hi Reinette,

On 5/3/24 18:33, Reinette Chatre wrote:
> Hi Babu,
> 
> On 3/28/2024 6:06 PM, Babu Moger wrote:
>> If the BMEC (Bandwidth Monitoring Event Configuration) feature is
>> supported, the bandwidth events can be configured to track specific events.
>> The event configuration is domain specific. ABMC (Assignable Bandwidth
>> Monitoring Counters) feature needs event configuration information to
>> assign RMID to the hardware counter. Currently, this information is not
>> available.
> 
> hmmm ... "Currently, this information is not available." does not sound
> accurate. Perhaps it can be made more specific with something like:
> "Event configurations are not stored in resctrl but instead always
> read from or written to hardware directly when prompted by user space."
> (feel free to improve)

ok. Sure

> 
>>
>> Save the event configuration information in the rdt_hw_domain, so it can
>> be used while for RMID assignment.
> 
> "be used while for RMID assignment" -> "be used for RMID assignment"?

Sure.

> 
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>>
>> ---
>> v3: Minor changes related to rebase in mbm_config_write_domain.
>>
>> v2: No changes.
>> ---
>>  arch/x86/kernel/cpu/resctrl/core.c     |  2 ++
>>  arch/x86/kernel/cpu/resctrl/internal.h |  3 +++
>>  arch/x86/kernel/cpu/resctrl/monitor.c  | 11 +++++++++++
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 +++++++++++++++-
>>  4 files changed, 31 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
>> index 50e9ec5e547b..ed4f6d49d737 100644
>> --- a/arch/x86/kernel/cpu/resctrl/core.c
>> +++ b/arch/x86/kernel/cpu/resctrl/core.c
>> @@ -555,6 +555,8 @@ static void domain_add_cpu(int cpu, struct rdt_resource *r)
>>  		return;
>>  	}
>>  
>> +	arch_domain_mbm_evt_config(hw_dom);
>> +
>>  	list_add_tail_rcu(&d->list, add_pos);
>>  
>>  	err = resctrl_online_domain(r, d);
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 41b06d46ea74..88453c86474b 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -385,6 +385,8 @@ struct rdt_hw_domain {
>>  	u32				*ctrl_val;
>>  	struct arch_mbm_state		*arch_mbm_total;
>>  	struct arch_mbm_state		*arch_mbm_local;
>> +	u32				mbm_total_cfg;
>> +	u32                             mbm_local_cfg;
> 
> (please fix tabs/spaces)

Ack.
> 
>>  };
>>  
>>  static inline struct rdt_hw_domain *resctrl_to_arch_dom(struct rdt_domain *r)
>> @@ -648,6 +650,7 @@ void __check_limbo(struct rdt_domain *d, bool force_free);
>>  void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
>>  void __init resctrl_file_fflags_init(const char *config,
>>  				     unsigned long fflags);
>> +void arch_domain_mbm_evt_config(struct rdt_hw_domain *hw_dom);
>>  void rdt_staged_configs_clear(void);
>>  bool closid_allocated(unsigned int closid);
>>  int resctrl_find_cleanest_closid(void);
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index 56dc49021540..8677dbf6de43 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -1090,3 +1090,14 @@ void __init intel_rdt_mbm_apply_quirk(void)
>>  	mbm_cf_rmidthreshold = mbm_cf_table[cf_index].rmidthreshold;
>>  	mbm_cf = mbm_cf_table[cf_index].cf;
>>  }
>> +
>> +void arch_domain_mbm_evt_config(struct rdt_hw_domain *hw_dom)
>> +{
>> +	if (mbm_total_event.configurable)
>> +		hw_dom->mbm_total_cfg = MAX_EVT_CONFIG_BITS;
>> +
>> +	if (mbm_local_event.configurable)
>> +		hw_dom->mbm_local_cfg = READS_TO_LOCAL_MEM |
>> +					NON_TEMP_WRITE_TO_LOCAL_MEM |
>> +					READS_TO_LOCAL_S_MEM;
>> +}
> 
> Shouldn't the defaults be discovered from hardware?

Yes. That is correct. We can read from the hardware.

-- 
Thanks
Babu Moger