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Date: Thu, 27 Jun 2024 16:26:31 -0500
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, babu.moger@....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 6/27/2024 3:56 PM, Reinette Chatre wrote:
> Hi Babu,
>
> On 6/27/24 11:51 AM, Moger, Babu wrote:
>> 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)
>
> The prefix for arch specific calls converged to "resctrl_arch_".
>
>> +{
>> + 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 expected that a call to set the event configuration on an architecture to
> also interact with the hardware. Essentially what mon_event_config_write()
> does today, but in addition also sets the cached
> mbm_total_cfg/mbm_local_cfg.
Yea. Understood.
>
> Part of this is done by the new MPAM portion [1]. With that the post-ABMC
> implementation of resctrl_arch_mon_event_config_read() may be what you
> have as arch_get_mbm_evt_cfg() above and
> resctrl_arch_mon_event_config_write()
> does the same as in [1] but with addition of updating the cached
> mbm_local_cfg/mbm_total_cfg within struct rdt_hw_domain. Would this work
> for ABMC?
Yes. It does work. I can keep the same name as well.
Thanks for the clarifications.
>
> Reinette
>
> [1]
> https://lore.kernel.org/lkml/20240614150033.10454-21-james.morse@arm.com/
>
>
--
- Babu Moger
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