Re: [PATCH v3 3/5] hw/acpi/aml-build: Build a root node in the PPTT table

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Apr 23, 2025 at 12:41:28PM +0100, Alireza Sanaee wrote:
> From: Yicong Yang <yangyicong@hisilicon.com>
> 
> 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>

so how does the topology look before and after this change?


> ---
>  hw/acpi/aml-build.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> index 560cee12a24b..3010325ca423 100644
> --- a/hw/acpi/aml-build.c
> +++ b/hw/acpi/aml-build.c
> @@ -2153,12 +2153,25 @@ 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 are separated

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().
> @@ -2175,7 +2188,7 @@ 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) {
> -- 
> 2.34.1