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Message-ID: <3d162f99-2fa8-4034-80a9-ea7ea43fda0b@amd.com>
Date: Fri, 22 Nov 2024 18:09:40 -0600
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, babu.moger@....com,
corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com
Cc: fenghua.yu@...el.com, x86@...nel.org, hpa@...or.com, thuth@...hat.com,
paulmck@...nel.org, rostedt@...dmis.org, akpm@...ux-foundation.org,
xiongwei.song@...driver.com, pawan.kumar.gupta@...ux.intel.com,
daniel.sneddon@...ux.intel.com, perry.yuan@....com, sandipan.das@....com,
kai.huang@...el.com, xiaoyao.li@...el.com, seanjc@...gle.com,
jithu.joseph@...el.com, brijesh.singh@....com, xin3.li@...el.com,
ebiggers@...gle.com, andrew.cooper3@...rix.com, mario.limonciello@....com,
james.morse@....com, tan.shaopeng@...itsu.com, tony.luck@...el.com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
peternewman@...gle.com, maciej.wieczor-retman@...el.com, eranian@...gle.com,
jpoimboe@...nel.org, thomas.lendacky@....com
Subject: Re: [PATCH v9 18/26] x86/resctrl: Add the interface to assign/update
counter assignment
Hi Reinette,
On 11/22/2024 4:07 PM, Reinette Chatre wrote:
> Hi Babu,
>
> On 11/22/24 1:04 PM, Moger, Babu wrote:
>> Hi Reinette,
>>
>> On 11/21/2024 2:50 PM, Reinette Chatre wrote:
>>> Hi Babu,
>>>
>>> On 11/20/24 10:05 AM, Moger, Babu wrote:
>>>> Hi Reinette,
>>>>
>>>> On 11/15/24 18:57, Reinette Chatre wrote:
>>>>> Hi Babu,
>>>>>
>>>>> On 10/29/24 4:21 PM, Babu Moger wrote:
>>>>>> The mbm_cntr_assign mode offers several hardware counters that can be
>>>>>> assigned to an RMID, event pair and monitor the bandwidth as long as it
>>>>>> is assigned.
>>>>>>
>>>>>> Counters are managed at two levels. The global assignment is tracked
>>>>>> using the mbm_cntr_free_map field in the struct resctrl_mon, while
>>>>>> domain-specific assignments are tracked using the mbm_cntr_map field
>>>>>> in the struct rdt_mon_domain. Allocation begins at the global level
>>>>>> and is then applied individually to each domain.
>>>>>>
>>>>>> Introduce an interface to allocate these counters and update the
>>>>>> corresponding domains accordingly.
>>>>>>
>>>>>> Signed-off-by: Babu Moger <babu.moger@....com>
>>>>>> ---
>>>>>
>>>>> ...
>>>>>
>>>>>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>>>>>> index 00f7bf60e16a..cb496bd97007 100644
>>>>>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>>>>>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>>>>>> @@ -717,6 +717,8 @@ unsigned int mon_event_config_index_get(u32 evtid);
>>>>>> int resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>>>>>> enum resctrl_event_id evtid, u32 rmid, u32 closid,
>>>>>> u32 cntr_id, bool assign);
>>>>>> +int rdtgroup_assign_cntr_event(struct rdt_resource *r, struct rdtgroup *rdtgrp,
>>>>>> + struct rdt_mon_domain *d, enum resctrl_event_id evtid);
>>>>>> 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/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>>>>> index 1b5529c212f5..bc3752967c44 100644
>>>>>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>>>>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>>>>> @@ -1924,6 +1924,93 @@ int resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>>>>>> return 0;
>>>>>> }
>>>>>> +/*
>>>>>> + * Configure the counter for the event, RMID pair for the domain.
>>>>>> + * Update the bitmap and reset the architectural state.
>>>>>> + */
>>>>>> +static int resctrl_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>>>>>> + enum resctrl_event_id evtid, u32 rmid, u32 closid,
>>>>>> + u32 cntr_id, bool assign)
>>>>>> +{
>>>>>> + int ret;
>>>>>> +
>>>>>> + ret = resctrl_arch_config_cntr(r, d, evtid, rmid, closid, cntr_id, assign);
>>>>>> + if (ret)
>>>>>> + return ret;
>>>>>> +
>>>>>> + if (assign)
>>>>>> + __set_bit(cntr_id, d->mbm_cntr_map);
>>>>>> + else
>>>>>> + __clear_bit(cntr_id, d->mbm_cntr_map);
>>>>>> +
>>>>>> + /*
>>>>>> + * Reset the architectural state so that reading of hardware
>>>>>> + * counter is not considered as an overflow in next update.
>>>>>> + */
>>>>>> + resctrl_arch_reset_rmid(r, d, closid, rmid, evtid);
>>>>>
>>>>> resctrl_arch_reset_rmid() expects to be run on a CPU that is in the domain
>>>>> @d ... note that after the architectural state is reset it initializes the
>>>>> state by reading the event on the current CPU. By running it here it is
>>>>> run on a random CPU that may not be in the right domain.
>>>>
>>>> Yes. That is correct. We can move this part to our earlier
>>>> implementation. We dont need to read the RMID. We just have to reset the
>>>> counter.
>>>>
>>>> https://lore.kernel.org/lkml/16d88cc4091cef1999b7ec329364e12dd0dc748d.1728495588.git.babu.moger@amd.com/
>>>>
>>>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>>> index 9fe419d0c536..bc3654ec3a08 100644
>>>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>>> @@ -2371,6 +2371,13 @@ int resctrl_arch_config_cntr(struct rdt_resource
>>>> *r, struct rdt_mon_domain *d,
>>>> smp_call_function_any(&d->hdr.cpu_mask, resctrl_abmc_config_one_amd,
>>>> &abmc_cfg, 1);
>>>>
>>>> + /*
>>>> + * Reset the architectural state so that reading of hardware
>>>> + * counter is not considered as an overflow in next update.
>>>> + */
>>>> + if (arch_mbm)
>>>> + memset(arch_mbm, 0, sizeof(struct arch_mbm_state));
>>>> +
>>>> return 0;
>>>> }
>>>>
>>>>
>>>
>>> I am not sure what you envision here. One motivation for the move out of
>>> resctrl_arch_config_cntr() was to avoid architectural state being reset twice. For reference,
>>> mbm_config_write_domain()->resctrl_arch_reset_rmid_all(). Will architectural state
>>> be reset twice again?
>>
>> That is good point. We don't have to do it twice.
>>
>> We can move the whole reset(arch_mbm) in resctrl_arch_config_cntr().
>
> This is not clear to me. The architectural state needs to be reset on MBM config write even
> when assignable mode is not supported and/or enabled. Moving it to resctrl_arch_config_cntr()
> will break this, no?
Yes. The architectural state needs to be reset if ABMC is enabled or not
enabled on MBM config write.
>
> I wonder if it may not simplify things to call resctrl_arch_reset_rmid() from
> resctrl_abmc_config_one_amd()?
Yes. That is is an option. I can try.
>
>>> One thing that I did not notice before is that the non-architectural MBM state is not
>>> reset. Care should be taken to reset this also when considering that there is a plan
>>> to use that MBM state to build a generic rate event for all platforms:
>>> https://lore.kernel.org/all/CALPaoCgFRFgQqG00Uc0GhMHK47bsbtFw6Bxy5O9A_HeYmGa5sA@mail.gmail.com/
>>
>> Did you mean we should add the following code in resctrl_arch_config_cntr()?
>>
>> m = get_mbm_state(d, closid, rmid, evtid);
>> if (m)
>> memset(m, 0, sizeof(struct mbm_state));
>
> This is not arch code but instead resctrl fs, so resctrl_config_cntr() may be more appropriate?
Sure. We can do that.
>
> Reinette
>
>
--
- Babu Moger
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