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

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Message-ID: <eb7f2b83-8d2a-753e-b7ab-9b004af2592d@amd.com>
Date: Tue, 16 Jul 2024 18:23:46 -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 7/12/2024 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.

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