linux-kernel - Re: [PATCH v1 24/31] x86/resctrl: Move get_config

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Date: Mon, 8 Apr 2024 20:25:26 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>
CC: Fenghua Yu <fenghua.yu@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, H Peter Anvin
	<hpa@...or.com>, Babu Moger <Babu.Moger@....com>,
	<shameerali.kolothum.thodi@...wei.com>, D Scott Phillips OS
	<scott@...amperecomputing.com>, <carl@...amperecomputing.com>,
	<lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
	<tan.shaopeng@...itsu.com>, <baolin.wang@...ux.alibaba.com>, Jamie Iles
	<quic_jiles@...cinc.com>, Xin Hao <xhao@...ux.alibaba.com>,
	<peternewman@...gle.com>, <dfustini@...libre.com>, <amitsinght@...vell.com>,
	David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
	"Dave Martin" <dave.martin@....com>
Subject: Re: [PATCH v1 24/31] x86/resctrl: Move get_config_index() to a header

Hi James,

On 3/21/2024 9:50 AM, James Morse wrote:
> get_config_index() is used by the architecture specific code to map a
> CLOSID+type pair to an index in the configuration arrays.
> 
> MPAM needs to do this too to preserve the ABI to user-space, there is
> no reason to do it differently.
> 
> Move the helper to a header file.
> 
> Signed-off-by: James Morse <james.morse@....com>
> ---
>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 19 +++----------------
>  include/linux/resctrl.h                   | 15 +++++++++++++++
>  2 files changed, 18 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index 3603ade95f1d..b4627ae19291 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -277,19 +277,6 @@ static int parse_line(char *line, struct resctrl_schema *s,
>  	return -EINVAL;
>  }
>  
> -static u32 get_config_index(u32 closid, enum resctrl_conf_type type)
> -{
> -	switch (type) {
> -	default:
> -	case CDP_NONE:
> -		return closid;
> -	case CDP_CODE:
> -		return closid * 2 + 1;
> -	case CDP_DATA:
> -		return closid * 2;
> -	}
> -}
> -
>  static bool apply_config(struct rdt_hw_domain *hw_dom,
>  			 struct resctrl_staged_config *cfg, u32 idx,
>  			 cpumask_var_t cpu_mask)
> @@ -311,7 +298,7 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_domain *d,
>  {
>  	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>  	struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
> -	u32 idx = get_config_index(closid, t);
> +	u32 idx = resctrl_get_config_index(closid, t);
>  	struct msr_param msr_param;
>  
>  	if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask))
> @@ -351,7 +338,7 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
>  			if (!cfg->have_new_ctrl)
>  				continue;
>  
> -			idx = get_config_index(closid, t);
> +			idx = resctrl_get_config_index(closid, t);
>  			if (!apply_config(hw_dom, cfg, idx, cpu_mask))
>  				continue;
>  
> @@ -476,7 +463,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_domain *d,
>  			    u32 closid, enum resctrl_conf_type type)
>  {
>  	struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
> -	u32 idx = get_config_index(closid, type);
> +	u32 idx = resctrl_get_config_index(closid, type);
>  
>  	return hw_dom->ctrl_val[idx];
>  }
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 3de5bc63ace0..73c111963433 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -258,6 +258,21 @@ bool resctrl_arch_is_evt_configurable(enum resctrl_event_id evt);
>  void resctrl_arch_mon_event_config_write(void *info);
>  void resctrl_arch_mon_event_config_read(void *info);
>  
> +/* For use by arch code to remap resctrl's smaller CDP CLOSID range */
> +static inline u32 resctrl_get_config_index(u32 closid,
> +					   enum resctrl_conf_type type)
> +{
> +	switch (type) {
> +	default:
> +	case CDP_NONE:
> +		return closid;
> +	case CDP_CODE:
> +			return (closid * 2) + 1;
> +	case CDP_DATA:
> +			return (closid * 2);
> +	}
> +}

(please check the tabs)

This change is unexpected to me. Could you please elaborate how
MPAM's variant of CDP works?

Thank you very much.

Reinette