Re: [PATCH v3 06/26] fs-x86/rectrl: Improve domain type checking

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Tony,

On 4/7/25 4:40 PM, Tony Luck wrote:
> The rdt_domain_hdr structure is used in both control and monitor
> domain structures to provide common methods for operations such as
> adding a CPU to a domain, removing a CPU from a domain, accessing
> the mask of all CPUs in a domain.
> 
> The "type" field provides a simple check whether a domain is a
> control or monitor domain so that programming errors operating
> on domains will be quickly caught.
> 
> To prepare for additional domain types that depend on the rdt_resource
> to which they are connected add the resource id into the type.
> 
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
>  include/linux/resctrl.h            | 19 ++++++++++---------
>  arch/x86/kernel/cpu/resctrl/core.c | 12 ++++++------
>  fs/resctrl/ctrlmondata.c           |  2 +-
>  3 files changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index d6a926b6fc0e..177f9879bae1 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -111,11 +111,6 @@ struct resctrl_staged_config {
>  	bool			have_new_ctrl;
>  };
>  
> -enum resctrl_domain_type {
> -	RESCTRL_CTRL_DOMAIN,
> -	RESCTRL_MON_DOMAIN,
> -};
> -
>  /**
>   * struct rdt_domain_hdr - common header for different domain types
>   * @list:		all instances of this resource
> @@ -124,12 +119,18 @@ enum resctrl_domain_type {
>   * @cpu_mask:		which CPUs share this resource
>   */
>  struct rdt_domain_hdr {
> -	struct list_head		list;
> -	int				id;
> -	enum resctrl_domain_type	type;
> -	struct cpumask			cpu_mask;
> +	struct list_head	list;
> +	int			id;
> +	u32			type;
> +	struct cpumask		cpu_mask;
>  };
>  
> +/* Bitfields in rdt_domain_hdr.type */
> +#define	DOMTYPE_RID		GENMASK(8, 0)
> +#define DOMTYPE_CTRL		BIT(9)
> +#define DOMTYPE_MON		BIT(10)
> +#define DOMTYPE(rid, type)	(((rid) & DOMTYPE_RID) | (type))
> +

This seems unnecessarily complicated to me. Why not just add the
resource id to the domain header?

Reinette