[PATCH v7 18/24] x86/resctrl: Auto Assign/unassign counters when mbm_cntr_assign is enabled

[Babu Moger <babu.moger@amd.com>]

Assign/unassign counters on resctrl group creation/deletion. Two counters
are required per group, one for MBM total event and one for MBM local
event.

There are a limited number of counters available for assignment. If these
counters are exhausted, the kernel will display the error message: "Out of
MBM assignable counters". However, it is not necessary to fail the
creation of a group due to assignment failures. Users have the flexibility
to modify the assignments at a later time.

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
v7: Reworded the commit message.
    Removed the reference of ABMC with mbm_cntr_assign.
    Renamed the function rdtgroup_assign_cntrs to rdtgroup_assign_grp.

v6: Removed the redundant comments on all the calls of
    rdtgroup_assign_cntrs. Updated the commit message.
    Dropped printing error message on every call of rdtgroup_assign_cntrs.

v5: Removed the code to enable/disable ABMC during the mount.
    That will be another patch.
    Added arch callers to get the arch specific data.
    Renamed fuctions to match the other abmc function.
    Added code comments for assignment failures.

v4: Few name changes based on the upstream discussion.
    Commit message update.

v3: This is a new patch. Patch addresses the upstream comment to enable
    ABMC feature by default if the feature is available.
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 61 ++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 21b9ca4ce493..bf94e4e05540 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2866,6 +2866,52 @@ static void schemata_list_destroy(void)
 	}
 }
 
+/*
+ * Called when a new group is created. If `mbm_cntr_assign` mode is enabled,
+ * counters are automatically assigned. Each group requires two counters:
+ * one for the total event and one for the local event. Due to the limited
+ * number of counters, assignments may fail in some cases. However, it is
+ * not necessary to fail the group creation. Users have the option to
+ * modify the assignments after the group has been created.
+ */
+static int rdtgroup_assign_grp(struct rdtgroup *rdtgrp)
+{
+	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
+	int ret = 0;
+
+	if (!resctrl_arch_mbm_cntr_assign_enabled(r))
+		return 0;
+
+	if (is_mbm_total_enabled())
+		ret = rdtgroup_assign_cntr(r, rdtgrp, NULL, QOS_L3_MBM_TOTAL_EVENT_ID);
+
+	if (!ret && is_mbm_local_enabled())
+		ret = rdtgroup_assign_cntr(r, rdtgrp, NULL, QOS_L3_MBM_LOCAL_EVENT_ID);
+
+	return ret;
+}
+
+/*
+ * Called when a group is deleted. Counters are unassigned if it was in
+ * assigned state.
+ */
+static int rdtgroup_unassign_grp(struct rdtgroup *rdtgrp)
+{
+	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
+	int ret = 0;
+
+	if (!resctrl_arch_mbm_cntr_assign_enabled(r))
+		return 0;
+
+	if (is_mbm_total_enabled())
+		ret = rdtgroup_unassign_cntr(r, rdtgrp, NULL, QOS_L3_MBM_TOTAL_EVENT_ID);
+
+	if (!ret && is_mbm_local_enabled())
+		ret = rdtgroup_unassign_cntr(r, rdtgrp, NULL, QOS_L3_MBM_LOCAL_EVENT_ID);
+
+	return ret;
+}
+
 static int rdt_get_tree(struct fs_context *fc)
 {
 	struct rdt_fs_context *ctx = rdt_fc2context(fc);
@@ -2925,6 +2971,8 @@ static int rdt_get_tree(struct fs_context *fc)
 		if (ret < 0)
 			goto out_mongrp;
 		rdtgroup_default.mon.mon_data_kn = kn_mondata;
+
+		rdtgroup_assign_grp(&rdtgroup_default);
 	}
 
 	ret = rdt_pseudo_lock_init();
@@ -2955,6 +3003,7 @@ static int rdt_get_tree(struct fs_context *fc)
 out_psl:
 	rdt_pseudo_lock_release();
 out_mondata:
+	rdtgroup_unassign_grp(&rdtgroup_default);
 	if (resctrl_arch_mon_capable())
 		kernfs_remove(kn_mondata);
 out_mongrp:
@@ -3214,6 +3263,8 @@ static void rdt_kill_sb(struct super_block *sb)
 		resctrl_arch_disable_alloc();
 	if (resctrl_arch_mon_capable())
 		resctrl_arch_disable_mon();
+
+	rdtgroup_unassign_grp(&rdtgroup_default);
 	resctrl_mounted = false;
 	kernfs_kill_sb(sb);
 	mutex_unlock(&rdtgroup_mutex);
@@ -3805,6 +3856,8 @@ static int rdtgroup_mkdir_mon(struct kernfs_node *parent_kn,
 		goto out_unlock;
 	}
 
+	rdtgroup_assign_grp(rdtgrp);
+
 	kernfs_activate(rdtgrp->kn);
 
 	/*
@@ -3849,6 +3902,8 @@ static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
 	if (ret)
 		goto out_closid_free;
 
+	rdtgroup_assign_grp(rdtgrp);
+
 	kernfs_activate(rdtgrp->kn);
 
 	ret = rdtgroup_init_alloc(rdtgrp);
@@ -3874,6 +3929,7 @@ static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
 out_del_list:
 	list_del(&rdtgrp->rdtgroup_list);
 out_rmid_free:
+	rdtgroup_unassign_grp(rdtgrp);
 	mkdir_rdt_prepare_rmid_free(rdtgrp);
 out_closid_free:
 	closid_free(closid);
@@ -3944,6 +4000,9 @@ static int rdtgroup_rmdir_mon(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
 	update_closid_rmid(tmpmask, NULL);
 
 	rdtgrp->flags = RDT_DELETED;
+
+	rdtgroup_unassign_grp(rdtgrp);
+
 	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
 
 	/*
@@ -3990,6 +4049,8 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
 	cpumask_or(tmpmask, tmpmask, &rdtgrp->cpu_mask);
 	update_closid_rmid(tmpmask, NULL);
 
+	rdtgroup_unassign_grp(rdtgrp);
+
 	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
 	closid_free(rdtgrp->closid);
 
-- 
2.34.1