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

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Date:   Tue, 22 Nov 2022 16:12:30 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Babu Moger <babu.moger@....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 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.

Reinette