linux-kernel - Re: [PATCH v2 06/17] x86/resctrl: Introduce interface to display number of ABMC counters

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Date: Tue, 20 Feb 2024 18:14:40 +0000
From: James Morse <james.morse@....com>
To: Babu Moger <babu.moger@....com>, corbet@....net, fenghua.yu@...el.com,
 reinette.chatre@...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
Subject: Re: [PATCH v2 06/17] x86/resctrl: Introduce interface to display
 number of ABMC counters

Hi Babu,

On 19/01/2024 18:22, Babu Moger wrote:
> The ABMC feature provides an option to the user to pin (or assign) the
> RMID to the hardware counter and monitor the bandwidth for a longer
> duration. There are only a limited number of hardware counters.
> 
> Provide the interface to display the number of ABMC counters supported.


> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index a6c336b6de61..fa492ea820f0 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -823,6 +823,10 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
>  			resctrl_file_fflags_init("mbm_local_bytes_config",
>  						 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
>  		}
> +

> +		if (rdt_cpu_has(X86_FEATURE_ABMC))

Please put this in a header and calling it something like
resctrl_arch_has_assignable_counters(). These X86 feature definition macros aren't
available on other architectures!


> +			resctrl_file_fflags_init("mbm_assignable_counters",
> +						 RFTYPE_MON_INFO);
>  	}
>  
>  	l3_mon_evt_init(r);
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 3e233251e7ed..53be5cd1c28e 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -811,6 +811,17 @@ static int rdtgroup_rmid_show(struct kernfs_open_file *of,
>  	return ret;
>  }
>  
> +static int rdtgroup_mbm_assignable_counters_show(struct kernfs_open_file *of,
> +						 struct seq_file *s, void *v)
> +{
> +	struct rdt_resource *r = of->kn->parent->priv;

> +	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);

(After the move out to /fs/ the resctrl_to_arch_res() macro is private to the arch code.
 Needing to do this when providing a value to user-space is the indication that the value
 should be in struct rdt_resource instead!)


> +	seq_printf(s, "%d\n", hw_res->mbm_assignable_counters);
> +
> +	return 0;
> +}
> +
>  #ifdef CONFIG_PROC_CPU_RESCTRL
>  
>  /*


Thanks,

James