linux-kernel - Re: [PATCH v5 18/20] x86/resctrl: Enable AMD ABMC feature by default when supported

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Message-ID: <9f46a7c1-818b-8847-1676-a86a31feedae@amd.com>
Date: Thu, 25 Jul 2024 19:16:58 -0500
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
 Babu Moger <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 v5 18/20] x86/resctrl: Enable AMD ABMC feature by default
 when supported

Hi Reinette,

On 7/16/2024 6:23 PM, Moger, Babu wrote:
> Hi Reinette,
> 
> On 7/12/2024 5:15 PM, Reinette Chatre wrote:
>> Hi Babu,
>>
>> On 7/3/24 2:48 PM, Babu Moger wrote:
>>> Enable ABMC by default when supported during the boot up.
>>>
>>> Users will not see any difference in the behavior when resctrl is
>>> mounted. With automatic assignment everything will work as running
>>> in the legacy monitor mode.
>>>
>>> Signed-off-by: Babu Moger <babu.moger@....com>
>>> ---
>>> v5: New patch to enable ABMC by default.
>>> ---
>>>   arch/x86/kernel/cpu/resctrl/core.c     |  2 ++
>>>   arch/x86/kernel/cpu/resctrl/internal.h |  1 +
>>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 17 +++++++++++++++++
>>>   3 files changed, 20 insertions(+)
>>>
>>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c 
>>> b/arch/x86/kernel/cpu/resctrl/core.c
>>> index 6265ef8b610f..b69b2650bde3 100644
>>> --- a/arch/x86/kernel/cpu/resctrl/core.c
>>> +++ b/arch/x86/kernel/cpu/resctrl/core.c
>>> @@ -599,6 +599,7 @@ static void domain_add_cpu_mon(int cpu, struct 
>>> rdt_resource *r)
>>>           d = container_of(hdr, struct rdt_mon_domain, hdr);
>>>           cpumask_set_cpu(cpu, &d->hdr.cpu_mask);
>>> +        resctrl_arch_configure_abmc();
>>>           return;
>>>       }
>>> @@ -620,6 +621,7 @@ static void domain_add_cpu_mon(int cpu, struct 
>>> rdt_resource *r)
>>>       arch_mon_domain_online(r, d);
>>>       resctrl_arch_mbm_evt_config(hw_dom);
>>> +    resctrl_arch_configure_abmc();
>>>       if (arch_domain_mbm_alloc(r->mon.num_rmid, hw_dom)) {
>>>           mon_domain_free(hw_dom);
>>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h 
>>> b/arch/x86/kernel/cpu/resctrl/internal.h
>>> index beb005775fe4..0f858cff8ab1 100644
>>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>>> @@ -707,6 +707,7 @@ void rdt_domain_reconfigure_cdp(struct 
>>> rdt_resource *r);
>>>   void __init resctrl_file_fflags_init(const char *config,
>>>                        unsigned long fflags);
>>>   void resctrl_arch_mbm_evt_config(struct rdt_hw_mon_domain *hw_dom);
>>> +void resctrl_arch_configure_abmc(void);
>>>   unsigned int mon_event_config_index_get(u32 evtid);
>>>   int resctrl_arch_assign_cntr(struct rdt_mon_domain *d, u32 evtid, 
>>> u32 rmid,
>>>                    u32 cntr_id, u32 closid, bool enable);
>>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c 
>>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>> index 531233779f8d..d978668c8865 100644
>>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>> @@ -2733,6 +2733,23 @@ void resctrl_arch_abmc_disable(void)
>>>       }
>>>   }
>>> +void resctrl_arch_configure_abmc(void)
>>> +{
>>> +    struct rdt_resource *r = 
>>> &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>>> +    struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>>> +    bool enable = true;
>>> +
>>> +    mutex_lock(&rdtgroup_mutex);
>>> +
>>> +    if (r->mon.abmc_capable) {
>>> +        if (!hw_res->abmc_enabled)
>>> +            hw_res->abmc_enabled = true;
>>> +        resctrl_abmc_set_one_amd(&enable);
>>> +    }
>>
>> This does not look right. It is not architecture code that needs to
>> decide if this feature is enabled or not, right? The feature is enabled
>> via fs (for example when user writes to mbm_mode). If the default is
>> enabled then it should be set by fs. resctrl_arch_configure_abmc()
>> then checks if feature is capable and enabled before it configures
>> it on the CPU.

Looking at the code again, I think it is fine to do it here. This is 
arch initialization code. I am checking if the feature is available and 
enable it by default. The fs code is not initialized yet at this stage.

Other option is to move everything to rdt_enable_ctx which is during the 
mount time.

I will keep it as is now. We can discuss more on this in v6.

> 
> That is correct. But this is a default setting should be done during the 
> initialization. This is like rdtgroup_setup_default(). I can move this 
> inside rdtgroup_init(void). I will have to change few things make sure 
> arch and fs code separate (like accessing abmc_enabled).
> Thanks
> - Babu Moger
> 

-- 
- Babu Moger