x86/intel_rdt: Fix exclusive mode handling of MBA resource

It is possible for a resource group to consist out of MBA as well as
CAT/CDP resources. The "exclusive" resource mode only applies to the
CAT/CDP resources since MBA allocations cannot be specified to overlap
or not. When a user requests a resource group to become "exclusive" then it
can only be successful if there are CAT/CDP resources in the group
and none of their CBMs associated with the group's CLOSID overlaps with
any other resource group.

Fix the "exclusive" mode setting by failing if there isn't any CAT/CDP
resource in the group and ensuring that the CBM checking is only done on
CAT/CDP resources.

Fixes: 49f7b4efa ("x86/intel_rdt: Enable setting of exclusive mode")
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H Peter Anvin" <hpa@zytor.com>
Cc: "Tony Luck" <tony.luck@intel.com>
Cc: "Xiaochen Shen" <xiaochen.shen@intel.com>
Cc: "Chen Yu" <yu.c.chen@intel.com>
Link: https://lkml.kernel.org/r/1537048707-76280-9-git-send-email-fenghua.yu@intel.com

arch/x86/kernel/cpu/intel_rdt_rdtgroup.c

@@ -1031,16 +1031,27 @@ static bool rdtgroup_mode_test_exclusive(struct rdtgroup *rdtgrp)
 {
 	int closid = rdtgrp->closid;
 	struct rdt_resource *r;
+	bool has_cache = false;
 	struct rdt_domain *d;
 
 	for_each_alloc_enabled_rdt_resource(r) {
+		if (r->rid == RDT_RESOURCE_MBA)
+			continue;
+		has_cache = true;
 		list_for_each_entry(d, &r->domains, list) {
 			if (rdtgroup_cbm_overlaps(r, d, d->ctrl_val[closid],
-						  rdtgrp->closid, false))
+						  rdtgrp->closid, false)) {
+				rdt_last_cmd_puts("schemata overlaps\n");
 				return false;
+			}
 		}
 	}
 
+	if (!has_cache) {
+		rdt_last_cmd_puts("cannot be exclusive without CAT/CDP\n");
+		return false;
+	}
+
 	return true;
 }
 
@@ -1092,7 +1103,6 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
 		rdtgrp->mode = RDT_MODE_SHAREABLE;
 	} else if (!strcmp(buf, "exclusive")) {
 		if (!rdtgroup_mode_test_exclusive(rdtgrp)) {
-			rdt_last_cmd_printf("schemata overlaps\n");
 			ret = -EINVAL;
 			goto out;
 		}