linux-kernel - Re: [PATCH v2 20/45] arm_mpam: resctrl: Implement helpers to update configuration

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Message-ID: <20260105175843.00007e35@huawei.com>
Date: Mon, 5 Jan 2026 17:58:43 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Ben Horgan <ben.horgan@....com>
CC: <amitsinght@...vell.com>, <baisheng.gao@...soc.com>,
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Subject: Re: [PATCH v2 20/45] arm_mpam: resctrl: Implement helpers to update
 configuration

On Fri, 19 Dec 2025 18:11:22 +0000
Ben Horgan <ben.horgan@....com> wrote:

> From: James Morse <james.morse@....com>
> 
> resctrl has two helpers for updating the configuration.
> resctrl_arch_update_one() updates a single value, and is used by the
> software-controller to apply feedback to the bandwidth controls, it has to
> be called on one of the CPUs in the resctrl:domain.
> 
> resctrl_arch_update_domains() copies multiple staged configurations, it can
> be called from anywhere.
> 
> Both helpers should update any changes to the underlying hardware.
> 
> Implement resctrl_arch_update_domains() to use
> resctrl_arch_update_one(). Neither need to be called on a specific CPU as
> the mpam driver will send IPIs as needed.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>
One trivial thing inline.

Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>

> ---
> list_for_each_entry -> list_for_each_entry_rcu
> return 0
> Restrict scope of local variables
> ---
>  drivers/resctrl/mpam_resctrl.c | 70 ++++++++++++++++++++++++++++++++++
>  1 file changed, 70 insertions(+)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 607e5f41f9e7..e5ec5438eca8 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -210,6 +210,76 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
>  	}
>  }
>  
> +int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_ctrl_domain *d,
> +			    u32 closid, enum resctrl_conf_type t, u32 cfg_val)
> +{
...

> +	partid = resctrl_get_config_index(closid, t);
> +	if (!r->alloc_capable || partid >= resctrl_arch_get_num_closid(r)) {
> +		pr_debug("Not alloc capable or computed PARTID out of range\n");
> +		return -EINVAL;
> +	}
> +
> +       /*

Spaces instead of a tab.

> +	* Copy the current config to avoid clearing other resources when the
> +	* same component is exposed multiple times through resctrl.
> +	*/