hw/acpi/aml-build: Only generate cluster node in PPTT when specified

Currently we'll always generate a cluster node no matter user has
specified '-smp clusters=X' or not. Cluster is an optional level
and will participant the building of Linux scheduling domains and
only appears on a few platforms. It's unncessary to always build
it when it cannot reflect the real topology on platforms having no
cluster implementation and to avoid affecting the linux scheduling
domains in the VM. So only generate the cluster topology in ACPI
PPTT when the user has specified it explicitly in -smp.

Tested qemu-system-aarch64 with `-smp 8` and linux 6.1-rc1, without
this patch:
estuary:/sys/devices/system/cpu/cpu0/topology$ cat cluster_*
ff	# cluster_cpus
0-7	# cluster_cpus_list
56	# cluster_id

with this patch:
estuary:/sys/devices/system/cpu/cpu0/topology$ cat cluster_*
ff	# cluster_cpus
0-7	# cluster_cpus_list
36	# cluster_id, with no cluster node kernel will make it to
	  physical package id

Acked-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Yanan Wang <[email protected]>
Tested-by: Yanan Wang <[email protected]>
Signed-off-by: Yicong Yang <[email protected]>
Message-Id: <20221229065513[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>

diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
index 42feb4d4d7f71c9f6f14f0ea6d3387cea5fab90a..ea331a20d131947b75ed7444d397448838f8fcb4 100644 (file)
--- a/hw/acpi/aml-build.c
+++ b/hw/acpi/aml-build.c
@@ -2030,7 +2030,7 @@ void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
                 0, socket_id, NULL, 0);
         }
 
-        if (mc->smp_props.clusters_supported) {
+        if (mc->smp_props.clusters_supported && mc->smp_props.has_clusters) {
             if (cpus->cpus[n].props.cluster_id != cluster_id) {
                 assert(cpus->cpus[n].props.cluster_id > cluster_id);
                 cluster_id = cpus->cpus[n].props.cluster_id;

diff --git a/hw/core/machine-smp.c b/hw/core/machine-smp.c
index b39ed21e65406563a012408240af228be4d74981..c3dab007dadc4e7bcaef9b244ea090ed6dc23bf8 100644 (file)
--- a/hw/core/machine-smp.c
+++ b/hw/core/machine-smp.c
@@ -158,6 +158,8 @@ void machine_parse_smp_config(MachineState *ms,
     ms->smp.threads = threads;
     ms->smp.max_cpus = maxcpus;
 
+    mc->smp_props.has_clusters = config->has_clusters;
+
     /* sanity-check of the computed topology */
     if (sockets * dies * clusters * cores * threads != maxcpus) {
         g_autofree char *topo_msg = cpu_hierarchy_to_string(ms);

diff --git a/include/hw/boards.h b/include/hw/boards.h
index d18d6d0073356123c6e1a691e76182195c838020..b0abbdd5dc217a68e751fdb0ddb325573f77bcb5 100644 (file)
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -130,11 +130,14 @@ typedef struct {
  * @prefer_sockets - whether sockets are preferred over cores in smp parsing
  * @dies_supported - whether dies are supported by the machine
  * @clusters_supported - whether clusters are supported by the machine
+ * @has_clusters - whether clusters are explicitly specified in the user
+ *                 provided SMP configuration
  */
 typedef struct {
     bool prefer_sockets;
     bool dies_supported;
     bool clusters_supported;
+    bool has_clusters;
 } SMPCompatProps;
 
 /**

diff --git a/qemu-options.hx b/qemu-options.hx
index 7f99d15b231fecc6c302bad610c576edde729339..8662568324bf0941a614cba8088bbab2775e9a3f 100644 (file)
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -343,6 +343,9 @@ SRST
     ::
 
         -smp 2
+
+    Note: The cluster topology will only be generated in ACPI and exposed
+    to guest if it's explicitly specified in -smp.
 ERST
 
 DEF("numa", HAS_ARG, QEMU_OPTION_numa,