diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 16b7bf5a048d66b810e23fed0b2760c96ea83d95..9f53b128bdb45c9341d652c1d427490240ab08a9 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -15,6 +15,8 @@
  * Software Developer Manual June 2016, volume 3, section 17.17.
  */
 
+#define pr_fmt(fmt)	"resctrl: " fmt
+
 #include <linux/cpu.h>
 #include <linux/module.h>
 #include <linux/sizes.h>
@@ -1110,6 +1112,68 @@ void arch_mon_domain_online(struct rdt_resource *r, struct rdt_mon_domain *d)
 		msr_clear_bit(MSR_RMID_SNC_CONFIG, 0);
 }
 
+/* CPU models that support MSR_RMID_SNC_CONFIG */
+static const struct x86_cpu_id snc_cpu_ids[] __initconst = {
+	X86_MATCH_VFM(INTEL_ICELAKE_X, 0),
+	X86_MATCH_VFM(INTEL_SAPPHIRERAPIDS_X, 0),
+	X86_MATCH_VFM(INTEL_EMERALDRAPIDS_X, 0),
+	X86_MATCH_VFM(INTEL_GRANITERAPIDS_X, 0),
+	X86_MATCH_VFM(INTEL_ATOM_CRESTMONT_X, 0),
+	{}
+};
+
+/*
+ * There isn't a simple hardware bit that indicates whether a CPU is running
+ * in Sub-NUMA Cluster (SNC) mode. Infer the state by comparing the
+ * number of CPUs sharing the L3 cache with CPU0 to the number of CPUs in
+ * the same NUMA node as CPU0.
+ * It is not possible to accurately determine SNC state if the system is
+ * booted with a maxcpus=N parameter. That distorts the ratio of SNC nodes
+ * to L3 caches. It will be OK if system is booted with hyperthreading
+ * disabled (since this doesn't affect the ratio).
+ */
+static __init int snc_get_config(void)
+{
+	struct cacheinfo *ci = get_cpu_cacheinfo_level(0, RESCTRL_L3_CACHE);
+	const cpumask_t *node0_cpumask;
+	int cpus_per_node, cpus_per_l3;
+	int ret;
+
+	if (!x86_match_cpu(snc_cpu_ids) || !ci)
+		return 1;
+
+	cpus_read_lock();
+	if (num_online_cpus() != num_present_cpus())
+		pr_warn("Some CPUs offline, SNC detection may be incorrect\n");
+	cpus_read_unlock();
+
+	node0_cpumask = cpumask_of_node(cpu_to_node(0));
+
+	cpus_per_node = cpumask_weight(node0_cpumask);
+	cpus_per_l3 = cpumask_weight(&ci->shared_cpu_map);
+
+	if (!cpus_per_node || !cpus_per_l3)
+		return 1;
+
+	ret = cpus_per_l3 / cpus_per_node;
+
+	/* sanity check: Only valid results are 1, 2, 3, 4 */
+	switch (ret) {
+	case 1:
+		break;
+	case 2 ... 4:
+		pr_info("Sub-NUMA Cluster mode detected with %d nodes per L3 cache\n", ret);
+		rdt_resources_all[RDT_RESOURCE_L3].r_resctrl.mon_scope = RESCTRL_L3_NODE;
+		break;
+	default:
+		pr_warn("Ignore improbable SNC node count %d\n", ret);
+		ret = 1;
+		break;
+	}
+
+	return ret;
+}
+
 int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 {
 	unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
@@ -1117,6 +1181,8 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 	unsigned int threshold;
 	int ret;
 
+	snc_nodes_per_l3_cache = snc_get_config();
+
 	resctrl_rmid_realloc_limit = boot_cpu_data.x86_cache_size * 1024;
 	hw_res->mon_scale = boot_cpu_data.x86_cache_occ_scale / snc_nodes_per_l3_cache;
 	r->num_rmid = (boot_cpu_data.x86_cache_max_rmid + 1) / snc_nodes_per_l3_cache;