linux-kernel - Re: [PATCH v8 05/13] x86/resctrl: Detect and configure Slow Memory Bandwidth Allocation

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Message-ID: <764c8eac-7b33-3850-3052-e6444ce496d0@amd.com>
Date:   Wed, 30 Nov 2022 12:43:29 -0600
From:   "Moger, Babu" <babu.moger@....com>
To:     Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de
Cc:     fenghua.yu@...el.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, paulmck@...nel.org, akpm@...ux-foundation.org,
        quic_neeraju@...cinc.com, rdunlap@...radead.org,
        damien.lemoal@...nsource.wdc.com, songmuchun@...edance.com,
        peterz@...radead.org, jpoimboe@...nel.org, pbonzini@...hat.com,
        chang.seok.bae@...el.com, pawan.kumar.gupta@...ux.intel.com,
        jmattson@...gle.com, daniel.sneddon@...ux.intel.com,
        sandipan.das@....com, tony.luck@...el.com, james.morse@....com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        bagasdotme@...il.com, eranian@...gle.com
Subject: Re: [PATCH v8 05/13] x86/resctrl: Detect and configure Slow Memory
 Bandwidth Allocation

Hi Reinette,

On 11/22/22 18:12, Reinette Chatre wrote:
> Hi Babu,
>
> On 11/4/2022 1:00 PM, Babu Moger wrote:
>> The QoS slow memory configuration details are available via
>> CPUID_Fn80000020_EDX_x02. Detect the available details and
>> initialize the rest to defaults.
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>>  arch/x86/kernel/cpu/resctrl/core.c        |   36 +++++++++++++++++++++++++++--
>>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c |    2 +-
>>  arch/x86/kernel/cpu/resctrl/internal.h    |    1 +
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c    |    8 ++++--
>>  4 files changed, 41 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
>> index e31c98e2fafc..6571d08e2b0d 100644
>> --- a/arch/x86/kernel/cpu/resctrl/core.c
>> +++ b/arch/x86/kernel/cpu/resctrl/core.c
>> @@ -162,6 +162,13 @@ bool is_mba_sc(struct rdt_resource *r)
>>  	if (!r)
>>  		return rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl.membw.mba_sc;
>>  
>> +	/*
>> +	 * The software controller support is only applicable to MBA resource.
>> +	 * Make sure to check for resource type again.
>> +	 */
> /again/d
>
> Not all callers of is_mba_sc() check if it is called for an MBA resource.
>
>> +	if (r->rid != RDT_RESOURCE_MBA)
>> +		return false;
>> +
>>  	return r->membw.mba_sc;
>>  }
>>  
>> @@ -225,9 +232,15 @@ static bool __rdt_get_mem_config_amd(struct rdt_resource *r)
>>  	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>>  	union cpuid_0x10_3_eax eax;
>>  	union cpuid_0x10_x_edx edx;
>> -	u32 ebx, ecx;
>> +	u32 ebx, ecx, subleaf;
>>  
>> -	cpuid_count(0x80000020, 1, &eax.full, &ebx, &ecx, &edx.full);
>> +	/*
>> +	 * Query CPUID_Fn80000020_EDX_x01 for MBA and
>> +	 * CPUID_Fn80000020_EDX_x02 for SMBA
>> +	 */
>> +	subleaf = (r->rid == RDT_RESOURCE_SMBA) ? 2 :  1;
>> +
>> +	cpuid_count(0x80000020, subleaf, &eax.full, &ebx, &ecx, &edx.full);
>>  	hw_res->num_closid = edx.split.cos_max + 1;
>>  	r->default_ctrl = MAX_MBA_BW_AMD;
>>  
>> @@ -750,6 +763,19 @@ static __init bool get_mem_config(void)
>>  	return false;
>>  }
>>  
>> +static __init bool get_slow_mem_config(void)
>> +{
>> +	struct rdt_hw_resource *hw_res = &rdt_resources_all[RDT_RESOURCE_SMBA];
>> +
>> +	if (!rdt_cpu_has(X86_FEATURE_SMBA))
>> +		return false;
>> +
>> +	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
>> +		return __rdt_get_mem_config_amd(&hw_res->r_resctrl);
>> +
>> +	return false;
>> +}
>> +
>>  static __init bool get_rdt_alloc_resources(void)
>>  {
>>  	struct rdt_resource *r;
>> @@ -780,6 +806,9 @@ static __init bool get_rdt_alloc_resources(void)
>>  	if (get_mem_config())
>>  		ret = true;
>>  
>> +	if (get_slow_mem_config())
>> +		ret = true;
>> +
>>  	return ret;
>>  }
>>  
>> @@ -869,6 +898,9 @@ static __init void rdt_init_res_defs_amd(void)
>>  		} else if (r->rid == RDT_RESOURCE_MBA) {
>>  			hw_res->msr_base = MSR_IA32_MBA_BW_BASE;
>>  			hw_res->msr_update = mba_wrmsr_amd;
>> +		} else if (r->rid == RDT_RESOURCE_SMBA) {
>> +			hw_res->msr_base = MSR_IA32_SMBA_BW_BASE;
>> +			hw_res->msr_update = mba_wrmsr_amd;
>>  		}
>>  	}
>>  }
> I mentioned earlier that this can be moved to init of
> rdt_resources_all[]. No strong preference, leaving here works
> also.

I am little confused about this comment. Initialization of
rdt_resources_all in core.c is mostly generic initialization. The msr_base
and msr_update routines here are vendor specific. I would prefer to keep
this in

rdt_init_res_defs_amd.Is that ok?

Thanks
Babu