hw/acpi/aml-build: Build a root node in the PPTT table

Currently we build the PPTT starting from the socket node and each
socket will be a separate tree. For a multi-socket system it'll
be hard for the OS to know the whole system is homogeneous or not
(actually we're in the current implementation) since no parent node
to telling the identical implementation informentation. Add a
root node for indicating this.

Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Alireza Sanaee <alireza.sanaee@huawei.com>
Message-Id: <20250714173146.511-4-alireza.sanaee@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
index 9b9be4ea0f5ffe6d4e10d8324ad3cbffca505f03..1e685f982f311ed79b5b7a8b3a318187d734b742 100644 (file)
--- a/hw/acpi/aml-build.c
+++ b/hw/acpi/aml-build.c
@@ -2152,12 +2152,25 @@ void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
     int64_t socket_id = -1, cluster_id = -1, core_id = -1;
     uint32_t socket_offset = 0, cluster_offset = 0, core_offset = 0;
     uint32_t pptt_start = table_data->len;
+    uint32_t root_offset;
     int n;
     AcpiTable table = { .sig = "PPTT", .rev = 2,
                         .oem_id = oem_id, .oem_table_id = oem_table_id };
 
     acpi_table_begin(&table, table_data);
 
+    /*
+     * Build a root node for all the processor nodes. Otherwise when
+     * building a multi-socket system each socket tree is separated
+     * and will be hard for the OS like Linux to know whether the
+     * system is homogeneous.
+     */
+    root_offset = table_data->len - pptt_start;
+    build_processor_hierarchy_node(table_data,
+        (1 << 0) | /* Physical package */
+        (1 << 4), /* Identical Implementation */
+        0, 0, NULL, 0);
+
     /*
      * This works with the assumption that cpus[n].props.*_id has been
      * sorted from top to down levels in mc->possible_cpu_arch_ids().
@@ -2174,7 +2187,7 @@ void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
             build_processor_hierarchy_node(table_data,
                 (1 << 0) | /* Physical package */
                 (1 << 4), /* Identical Implementation */
-                0, socket_id, NULL, 0);
+                root_offset, socket_id, NULL, 0);
         }
 
         if (mc->smp_props.clusters_supported && mc->smp_props.has_clusters) {