linux-kernel - Re: [PATCH v2 13/23] x86/resctrl: Allow update_mba

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Date:   Fri, 15 Oct 2021 15:28:22 -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>,
        Jamie Iles <jamie@...iainc.com>,
        "D Scott Phillips OS" <scott@...amperecomputing.com>,
        <lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
        <tan.shaopeng@...itsu.com>
Subject: Re: [PATCH v2 13/23] x86/resctrl: Allow update_mba_bw() to update
 controls directly

Hi James,

On 10/1/2021 9:02 AM, James Morse wrote:

...

> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index 9f45207a6c74..25baacd331e0 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -282,6 +282,27 @@ static bool apply_config(struct rdt_hw_domain *hw_dom,
>   	return false;
>   }
>   
> +int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_domain *d,
> +			    u32 closid, enum resctrl_conf_type t, u32 cfg_val)
> +{
> +	struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
> +	u32 idx = get_config_index(closid, t);
> +	struct msr_param msr_param;
> +
> +	if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask))
> +		return -EINVAL;
> +
> +	hw_dom->ctrl_val[idx] = cfg_val;
> +
> +	msr_param.res = r;
> +	msr_param.low = idx;
> +	msr_param.high = idx + 1;
> +
> +	rdt_ctrl_update(&msr_param);
> +

rdt_ctrl_update() will take its parameters and recompute the domain that 
is already available here ... seems to take a few steps back and then do 
the needed. Could msr_update be called directly here instead?

Reinette