linux-kernel - Re: [PATCH v4 11/19] x86/resctrl: Introduce mbm_total_cfg and mbm_local

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Date: Thu, 27 Jun 2024 13:51:30 -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: [PATCH v4 11/19] x86/resctrl: Introduce mbm_total_cfg and
 mbm_local_cfg

Hi Reinette,

On 6/13/24 20:43, Reinette Chatre wrote:
> Hi Babu,
> 
> On 5/24/24 5:23 AM, 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 hardware counter to an RMID. Event configurations
>> are not stored in resctrl but instead always read from or written to
>> hardware directly when prompted by user space.
>>
>> Read the event configuration from the hardware during the domain
>> initialization. Save the configuration information in the rdt_hw_domain,
>> so it can be used for counter assignment.
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> v4: Read the configuration information from the hardware to initialize.
>>      Added few commit messages.
>>      Fixed the tab spaces.
>>
>> 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 |  5 +++++
>>   arch/x86/kernel/cpu/resctrl/monitor.c  | 21 +++++++++++++++++++++
>>   3 files changed, 28 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c
>> b/arch/x86/kernel/cpu/resctrl/core.c
>> index ec93f6a50308..856c46d12177 100644
>> --- a/arch/x86/kernel/cpu/resctrl/core.c
>> +++ b/arch/x86/kernel/cpu/resctrl/core.c
>> @@ -542,6 +542,8 @@ 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 5e7e76cd512f..60a1ca0a11a7 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -373,6 +373,8 @@ struct arch_mbm_state {
>>    * @ctrl_val:    array of cache or mem ctrl values (indexed by CLOSID)
>>    * @arch_mbm_total:    arch private state for MBM total bandwidth
>>    * @arch_mbm_local:    arch private state for MBM local bandwidth
>> + * @mbm_total_cfg:    MBM total bandwidth configuration
>> + * @mbm_local_cfg:    MBM local bandwidth configuration
>>    *
>>    * Members of this structure are accessed via helpers that provide
>> abstraction.
>>    */
>> @@ -381,6 +383,8 @@ 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;
>>   };
> 
> Similar to the abmc_enabled member of rdt_hw_resource, these new
> members of rdt_hw_domain are architecture specific and should never be
> touched directly by resctrl fs code, for example, from mbm_config_show().

Need some clarification here.

I am thinking you want to introduce architecture specific routines to get
and set mbm_total_config/mbm_local_config for the domain.
Something like this.

+int arch_get_mbm_evt_cfg(struct rdt_domain *d, enum resctrl_event_id eventid)
+{
+       struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
+
+       switch (eventid) {
+       case QOS_L3_OCCUP_EVENT_ID:
+               break;
+       case QOS_L3_MBM_TOTAL_EVENT_ID:
+               return hw_dom->mbm_total_cfg;
+       case QOS_L3_MBM_LOCAL_EVENT_ID:
+               return hw_dom->mbm_local_cfg;
+       }
+
+       /* Never expect to get here */
+       WARN_ON_ONCE(1);
+
+       return -1;
+}
+
+void arch_set_mbm_evt_cfg(struct rdt_domain *d,
+                         enum resctrl_event_id eventid, u32 val)
+{
+       struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
+
+       switch (eventid) {
+       case QOS_L3_OCCUP_EVENT_ID:
+               break;
+       case QOS_L3_MBM_TOTAL_EVENT_ID:
+               hw_dom->mbm_total_cfg = val;
+               break;
+       case QOS_L3_MBM_LOCAL_EVENT_ID:
+               hw_dom->mbm_local_cfg = val;
+       }
+
+       return;
+}
+

I have added the functions in rdtgroup.c and prototypes in internal.h.
This will be called in mbm)config_show() and mbm_config_write_domain()

Did I understand this correctly?

Thanks
Babu