[PATCH v12 24/26] x86/resctrl: Introduce the interface to modify assignments in a group

[Babu Moger]

Introduce an interface to modify assignments within a group.

Modifications follow this format:
<Event configuration>:<Domain id>=<Assignment type>

The assignment type can be one of the following:

_ : No event configuration assigned

e : Event configuration assigned in exclusive mode

Domain id can be any valid domain ID number or '*' to update all the
domains.

Example:
$cd /sys/fs/resctrl
$cat mbm_L3_assignments
mbm_total_bytes:0=e;1=e
mbm_local_bytes:0=e;1=e

To unassign the configuration of mbm_total_bytes on domain 0:

$echo "mbm_total_bytes:0=_" > mbm_L3_assignments
$cat mbm_L3_assignments
mbm_total_bytes:0=_;1=e
mbm_local_bytes:0=e;1=e

To unassign the mbm_total_bytes configuration on all domains:

$echo "mbm_total_bytes:*=_" > mbm_L3_assignments
$cat mbm_L3_assignments
mbm_total_bytes:0=_;1=_
mbm_local_bytes:0=e;1=e

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v12: New patch:
     Assignment interface moved inside the group based the discussion
     https://lore.kernel.org/lkml/CALPaoCiii0vXOF06mfV=kVLBzhfNo0SFqt4kQGwGSGVUqvr2Dg@xxxxxxxxxxxxxx/#t
---
 Documentation/arch/x86/resctrl.rst     |  29 ++++-
 arch/x86/kernel/cpu/resctrl/internal.h |   9 ++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 162 ++++++++++++++++++++++++-
 3 files changed, 198 insertions(+), 2 deletions(-)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 31085b4e15f6..ad35c38eed34 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -514,7 +514,7 @@ When the "mba_MBps" mount option is used all CTRL_MON groups will also contain:
 	Event configuration: A valid event configuration listed in the
 	/sys/fs/resctrl/info/L3_MON/counter_configs directory.
 
-	Domain ID: A valid domain ID number.
+	Domain ID: A valid domain ID number or '*' to update all the domains.
 
 	Assignment types:
 
@@ -530,6 +530,33 @@ When the "mba_MBps" mount option is used all CTRL_MON groups will also contain:
 	 mbm_total_bytes:0=e;1=e
 	 mbm_local_bytes:0=e;1=e
 
+	The assignments can be modified by writing to the interface.
+
+	Example:
+	To unassign the configuration of mbm_total_bytes on domain 0:
+	::
+
+	 # echo "mbm_total_bytes:0=_" > mbm_L3_assignments
+	 # cat mbm_L3_assignments
+	 mbm_total_bytes:0=_;1=e
+	 mbm_local_bytes:0=e;1=e
+
+	To unassign the mbm_total_bytes configuration on all domains:
+	::
+
+	 # echo "mbm_total_bytes:*=_" > mbm_L3_assignments
+	 # cat mbm_L3_assignments
+	 mbm_total_bytes:0=_;1=_
+	 mbm_local_bytes:0=e;1=e
+
+	To assign the mbm_total_bytes configuration on all domains in exclusive mode:
+	::
+
+	 # echo "mbm_total_bytes:*=e" > mbm_L3_assignments
+	 # cat mbm_L3_assignments
+	 mbm_total_bytes:0=e;1=e
+	 mbm_local_bytes:0=e;1=e
+
 Resource allocation rules
 -------------------------
 
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index a943450bf2c8..2020a2fe7135 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -44,6 +44,15 @@
 #define ABMC_EXTENDED_EVT_ID		BIT(31)
 #define ABMC_EVT_ID			1
 
+/*
+ * Assignment types for mbm_cntr_assign mode
+ */
+enum {
+	ASSIGN_NONE		= 0,
+	ASSIGN_EXCLUSIVE,
+	ASSIGN_INVALID,
+};
+
 /**
  * cpumask_any_housekeeping() - Choose any CPU in @mask, preferring those that
  *			        aren't marked nohz_full
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index ee1c949c2436..5d9c4c216522 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -84,6 +84,18 @@ static struct mbm_assign_config *mbm_get_assign_config(enum resctrl_event_id evt
 	return NULL;
 }
 
+static struct mbm_assign_config *mbm_get_assign_config_by_name(char *config)
+{
+	int i;
+
+	for (i = 0; i < NUM_MBM_ASSIGN_CONFIGS; i++) {
+		if (!strcmp(mbm_assign_configs[i].name, config))
+			return &mbm_assign_configs[i];
+	}
+
+	return NULL;
+}
+
 /*
  * Used to store the max resource name width to display the schemata names in
  * a tabular format.
@@ -2125,6 +2137,153 @@ static int mbm_L3_assignments_show(struct kernfs_open_file *of, struct seq_file
 	return ret;
 }
 
+static unsigned int resctrl_get_assing_type(char *assign)
+{
+	unsigned int mon_state = ASSIGN_NONE;
+	int len = strlen(assign);
+
+	if (!len || len > 1)
+		return ASSIGN_INVALID;
+
+	switch (*assign) {
+	case 'e':
+		mon_state = ASSIGN_EXCLUSIVE;
+		break;
+	case '_':
+		mon_state = ASSIGN_NONE;
+		break;
+	default:
+		mon_state = ASSIGN_INVALID;
+		break;
+	}
+
+	return mon_state;
+}
+
+static int resctrl_process_assign(struct rdt_resource *r, struct rdtgroup *rdtgrp,
+				  char *config, char *tok)
+{
+	struct mbm_assign_config *assign_config;
+	struct rdt_mon_domain *d;
+	char *dom_str, *id_str;
+	unsigned long dom_id = 0;
+	int assign_type;
+	char domain[10];
+	bool found;
+	int ret;
+
+	assign_config = mbm_get_assign_config_by_name(config);
+	if (!assign_config) {
+		rdt_last_cmd_printf("Invalid assign configuration %s\n", config);
+		return  -ENOENT;
+	}
+
+next:
+	if (!tok || tok[0] == '\0')
+		return 0;
+
+	/* Start processing the strings for each domain */
+	dom_str = strim(strsep(&tok, ";"));
+
+	id_str = strsep(&dom_str, "=");
+
+	/* Check for domain id '*' which means all domains */
+	if (id_str && *id_str == '*') {
+		d = NULL;
+		goto check_state;
+	} else if (!id_str || kstrtoul(id_str, 10, &dom_id)) {
+		rdt_last_cmd_puts("Missing domain id\n");
+		return -EINVAL;
+	}
+
+	/* Verify if the dom_id is valid */
+	found = false;
+	list_for_each_entry(d, &r->mon_domains, hdr.list) {
+		if (d->hdr.id == dom_id) {
+			found = true;
+			break;
+		}
+	}
+
+	if (!found) {
+		rdt_last_cmd_printf("Invalid domain id %ld\n", dom_id);
+		return -EINVAL;
+	}
+
+check_state:
+	assign_type = resctrl_get_assing_type(dom_str);
+
+	switch (assign_type) {
+	case ASSIGN_NONE:
+		ret = resctrl_unassign_cntr_event(r, d, rdtgrp, assign_config->evtid,
+						  assign_config->val);
+		break;
+	case ASSIGN_EXCLUSIVE:
+		ret = resctrl_assign_cntr_event(r, d, rdtgrp, assign_config->evtid,
+						assign_config->val);
+		break;
+	case ASSIGN_INVALID:
+		ret = -EINVAL;
+	}
+
+	if (ret)
+		goto out_fail;
+
+	goto next;
+
+out_fail:
+	sprintf(domain, d ? "%ld" : "*", dom_id);
+
+	rdt_last_cmd_printf("Assign operation '%s:%s=%s' failed\n", config, domain, dom_str);
+
+	return ret;
+}
+
+static ssize_t mbm_L3_assignments_write(struct kernfs_open_file *of, char *buf,
+					size_t nbytes, loff_t off)
+{
+	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
+	struct rdtgroup *rdtgrp;
+	char *token, *config;
+	int ret = 0;
+
+	/* Valid input requires a trailing newline */
+	if (nbytes == 0 || buf[nbytes - 1] != '\n')
+		return -EINVAL;
+
+	buf[nbytes - 1] = '\0';
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (!rdtgrp) {
+		rdtgroup_kn_unlock(of->kn);
+		return -ENOENT;
+	}
+	rdt_last_cmd_clear();
+
+	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
+		rdt_last_cmd_puts("mbm_cntr_assign mode is not enabled\n");
+		rdtgroup_kn_unlock(of->kn);
+		return -EINVAL;
+	}
+
+	while ((token = strsep(&buf, "\n")) != NULL) {
+		/*
+		 * The write command follows the following format:
+		 * “<Assign config>:<domain_id>=<assign mode>”
+		 * Extract Assign config first.
+		 */
+		config = strsep(&token, ":");
+
+		ret = resctrl_process_assign(r, rdtgrp, config, token);
+		if (ret)
+			break;
+	}
+
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret ?: nbytes;
+}
+
 /* rdtgroup information files for one cache resource. */
 static struct rftype res_common_files[] = {
 	{
@@ -2246,9 +2405,10 @@ static struct rftype res_common_files[] = {
 	},
 	{
 		.name		= "mbm_L3_assignments",
-		.mode		= 0444,
+		.mode		= 0644,
 		.kf_ops		= &rdtgroup_kf_single_ops,
 		.seq_show	= mbm_L3_assignments_show,
+		.write		= mbm_L3_assignments_write,
 	},
 	{
 		.name		= "mbm_assign_mode",
-- 
2.34.1