[PATCH v6 2/2] fs/resctrl: Add "*" shorthand to set io_alloc CBM for all domains

[Aaron Tomlin <atomlin@atomlin.com>]

Configuring the io_alloc_cbm interface requires an explicit domain ID
for each cache domain. On systems with high core counts and numerous
cache clusters, this requirement becomes cumbersome for automation and
management tasks that aim to apply a uniform policy.

Introduce a wildcard domain ID selector "*" for the io_alloc_cbm
interface. This enables users to set the same Capacity Bitmask (CBM)
across all cache domains in a single operation.

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
 Documentation/filesystems/resctrl.rst |  8 ++++++++
 fs/resctrl/ctrlmondata.c              | 21 +++++++++++++++++----
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index ba609f8d4de5..b003bed339fd 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
 
+		An ID of "*" configures all domains with the provided CBM.
+
+		Example on a system that does not require a minimum number of consecutive bits in the mask::
+
+			# echo "*=0" > /sys/fs/resctrl/info/L3/io_alloc_cbm
+			# cat /sys/fs/resctrl/info/L3/io_alloc_cbm
+			0=0;1=0
+
 		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 2ef53161ce11..9a7dfc48cb2e 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -954,25 +954,34 @@ static int resctrl_io_alloc_parse_line(char *line,  struct rdt_resource *r,
 				       struct resctrl_schema *s, u32 closid)
 {
 	enum resctrl_conf_type peer_type;
+	unsigned long dom_id = ULONG_MAX;
 	struct rdt_parse_data data;
 	struct rdt_ctrl_domain *d;
+	bool update_all = false;
 	char *dom = NULL, *id;
-	unsigned long dom_id;
 
 next:
 	if (!line || line[0] == '\0')
 		return 0;
 
+	if (update_all) {
+		rdt_last_cmd_puts("Configurations after global '*'\n");
+		return -EINVAL;
+	}
+
 	dom = strsep(&line, ";");
 	id = strsep(&dom, "=");
-	if (!dom || kstrtoul(id, 10, &dom_id)) {
+
+	if (dom && !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);
 	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;
@@ -988,10 +997,14 @@ 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;
+
 	rdt_last_cmd_printf("Invalid domain %lu\n", dom_id);
 	return -EINVAL;
 }
-- 
2.51.0