Re: [v4 PATCH 1/1] x86/resctrl: Add "*" shorthand to set io_alloc CBM for all domains

[Babu Moger <bmoger@amd.com>]

Hi Aaron,


On 1/25/26 11:17, Aaron Tomlin wrote:
> Introduce a wildcard domain ID selector "*" for the io_alloc_cbm
> interface. This allows a user to update the Capacity Bitmask (CBM)
> across all cache domains in a single operation.
>
> Currently, configuring io_alloc_cbm requires an explicit ID for each
> domain, which is cumbersome on systems with high core counts and
> numerous cache clusters. Supporting a wildcard selector simplifies
> automation and management tasks.
>
> For example, a user can now write "*=0" to the io_alloc_cbm file to
> program every domain to the hardware-defined minimum CBM. Note that the
> value provided must still adhere to the constraints defined in the
> resource's min_cbm_bits.
>
> Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
> ---
>   Documentation/filesystems/resctrl.rst |  8 ++++++++
>   fs/resctrl/ctrlmondata.c              | 20 +++++++++++++++++---
>   2 files changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 8c8ce678148a..734aba0d19fd 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -215,6 +215,14 @@ related to allocation:
>   			# cat /sys/fs/resctrl/info/L3/io_alloc_cbm
>   			0=00ff;1=000f
>   
> +		Set each CBM to a specified value.
> +
> +		An ID of "*" configures all domains with the provided CBM.
> +
> +		Example::
> +
> +			# echo "*=0" > /sys/fs/resctrl/info/L3/io_alloc_cbm
> +

You missed adding

# cat /sys/fs/resctrl/info/L3/io_alloc_cbm
  0=0;1=0

Thanks

Babu

>   		When CDP is enabled "io_alloc_cbm" associated with the CDP_DATA and CDP_CODE
>   		resources may reflect the same values. For example, values read from and
>   		written to /sys/fs/resctrl/info/L3DATA/io_alloc_cbm may be reflected by
> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
> index b2d178d3556e..f5fb74a7668a 100644
> --- a/fs/resctrl/ctrlmondata.c
> +++ b/fs/resctrl/ctrlmondata.c
> @@ -873,21 +873,31 @@ static int resctrl_io_alloc_parse_line(char *line,  struct rdt_resource *r,
>   	struct rdt_ctrl_domain *d;
>   	char *dom = NULL, *id;
>   	unsigned long dom_id;
> +	bool update_all;
>   
>   next:
>   	if (!line || line[0] == '\0')
>   		return 0;
>   
> +	update_all = false;
>   	dom = strsep(&line, ";");
>   	id = strsep(&dom, "=");
> -	if (!dom || kstrtoul(id, 10, &dom_id)) {
> +
> +	if (id && !strcmp(id, "*")) {
> +		update_all = true;
> +	} else if (!dom || kstrtoul(id, 10, &dom_id)) {
>   		rdt_last_cmd_puts("Missing '=' or non-numeric domain\n");
>   		return -EINVAL;
>   	}
>   
>   	dom = strim(dom);
> +	if (update_all && !dom) {
> +		rdt_last_cmd_puts("Missing '=' after '*'\n");
> +		return -EINVAL;
> +	}
> +
>   	list_for_each_entry(d, &r->ctrl_domains, hdr.list) {
> -		if (d->hdr.id == dom_id) {
> +		if (update_all || d->hdr.id == dom_id) {
>   			data.buf = dom;
>   			data.mode = RDT_MODE_SHAREABLE;
>   			data.closid = closid;
> @@ -903,10 +913,14 @@ static int resctrl_io_alloc_parse_line(char *line,  struct rdt_resource *r,
>   				       &d->staged_config[s->conf_type],
>   				       sizeof(d->staged_config[0]));
>   			}
> -			goto next;
> +			if (!update_all)
> +				goto next;
>   		}
>   	}
>   
> +	if (update_all)
> +		goto next;
> +
>   	return -EINVAL;
>   }
>