hw/arm/sbsa-ref: Enable CPU cluster on ARM sbsa machine

Enable CPU cluster support on SbsaQemu platform, so that users can
specify a 4-level CPU hierarchy sockets/clusters/cores/threads. And
this topology can be passed to the firmware through /cpus/topology
Device Tree.

Signed-off-by: Xiong Yining <xiongyining1480@phytium.com.cn>
Reviewed-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>
Message-id: 20240607103825.1295328-2-xiongyining1480@phytium.com.cn
Tested-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

docs/system/arm/sbsa.rst

@@ -62,6 +62,7 @@ The devicetree reports:
    - platform version
    - GIC addresses
    - NUMA node id for CPUs and memory
+   - CPU topology information
 
 Platform version
 ''''''''''''''''
@@ -88,3 +89,6 @@ Platform version changes:
 
 0.3
   The USB controller is an XHCI device, not EHCI.
+
+0.4
+  CPU topology information is present in devicetree.

hw/arm/sbsa-ref.c

@@ -219,7 +219,7 @@ static void create_fdt(SBSAMachineState *sms)
      *                        fw compatibility.
      */
     qemu_fdt_setprop_cell(fdt, "/", "machine-version-major", 0);
-    qemu_fdt_setprop_cell(fdt, "/", "machine-version-minor", 3);
+    qemu_fdt_setprop_cell(fdt, "/", "machine-version-minor", 4);
 
     if (ms->numa_state->have_numa_distance) {
         int size = nb_numa_nodes * nb_numa_nodes * 3 * sizeof(uint32_t);
@@ -276,6 +276,14 @@ static void create_fdt(SBSAMachineState *sms)
         g_free(nodename);
     }
 
+    /* Add CPU topology description through fdt node topology. */
+    qemu_fdt_add_subnode(sms->fdt, "/cpus/topology");
+
+    qemu_fdt_setprop_cell(sms->fdt, "/cpus/topology", "sockets", ms->smp.sockets);
+    qemu_fdt_setprop_cell(sms->fdt, "/cpus/topology", "clusters", ms->smp.clusters);
+    qemu_fdt_setprop_cell(sms->fdt, "/cpus/topology", "cores", ms->smp.cores);
+    qemu_fdt_setprop_cell(sms->fdt, "/cpus/topology", "threads", ms->smp.threads);
+
     sbsa_fdt_add_gic_node(sms);
 }
 
@@ -898,6 +906,7 @@ static void sbsa_ref_class_init(ObjectClass *oc, void *data)
     mc->default_ram_size = 1 * GiB;
     mc->default_ram_id = "sbsa-ref.ram";
     mc->default_cpus = 4;
+    mc->smp_props.clusters_supported = true;
     mc->possible_cpu_arch_ids = sbsa_ref_possible_cpu_arch_ids;
     mc->cpu_index_to_instance_props = sbsa_ref_cpu_index_to_props;
     mc->get_default_cpu_node_id = sbsa_ref_get_default_cpu_node_id;