Re: [PATCH v7 4/4] hw/acpi/aml-build: Use existing CPU topology to build PPTT table

["wangyanan (Y)" via <qemu-devel@nongnu.org>]

Hi Gavin,

On 2022/4/20 18:49, Gavin Shan wrote:
> When the PPTT table is built, the CPU topology is re-calculated, but
> it's unecessary because the CPU topology has been populated in
> virt_possible_cpu_arch_ids() on arm/virt machine.
>
> This reworks build_pptt() to avoid by reusing the existing IDs in
> ms->possible_cpus. Currently, the only user of build_pptt() is
> arm/virt machine.
>
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>   hw/acpi/aml-build.c | 109 +++++++++++++++++++-------------------------
>   1 file changed, 47 insertions(+), 62 deletions(-)
>
> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> index 4086879ebf..73f4e69c29 100644
> --- a/hw/acpi/aml-build.c
> +++ b/hw/acpi/aml-build.c
> @@ -2002,86 +2002,71 @@ void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
>                   const char *oem_id, const char *oem_table_id)
>   {
>       MachineClass *mc = MACHINE_GET_CLASS(ms);
> -    GQueue *list = g_queue_new();
> -    guint pptt_start = table_data->len;
> -    guint parent_offset;
> -    guint length, i;
> -    int uid = 0;
> -    int socket;
> +    CPUArchIdList *cpus = ms->possible_cpus;
> +    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;
> +    int n;
>       AcpiTable table = { .sig = "PPTT", .rev = 2,
>                           .oem_id = oem_id, .oem_table_id = oem_table_id };
>   
>       acpi_table_begin(&table, table_data);
>   
> -    for (socket = 0; socket < ms->smp.sockets; socket++) {
> -        g_queue_push_tail(list,
> -            GUINT_TO_POINTER(table_data->len - pptt_start));
> -        build_processor_hierarchy_node(
> -            table_data,
> -            /*
> -             * Physical package - represents the boundary
> -             * of a physical package
> -             */
> -            (1 << 0),
> -            0, socket, 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().
> +     * Otherwise, the unexpected and duplicate containers will be
> +     * created.
> +     */
s/duplicate/duplicated
> +    for (n = 0; n < cpus->len; n++) {
> +        if (cpus->cpus[n].props.socket_id != socket_id) {
> +            assert(cpus->cpus[n].props.socket_id > socket_id);
> +            socket_id = cpus->cpus[n].props.socket_id;
> +            cluster_id = -1;
> +            core_id = -1;
> +            socket_offset = table_data->len - pptt_start;
> +            build_processor_hierarchy_node(table_data,
> +                (1 << 0), /* Physical package */
> +                0, socket_id, NULL, 0);
> +        }
>   
> -    if (mc->smp_props.clusters_supported) {
> -        length = g_queue_get_length(list);
> -        for (i = 0; i < length; i++) {
> -            int cluster;
> -
> -            parent_offset = GPOINTER_TO_UINT(g_queue_pop_head(list));
> -            for (cluster = 0; cluster < ms->smp.clusters; cluster++) {
> -                g_queue_push_tail(list,
> -                    GUINT_TO_POINTER(table_data->len - pptt_start));
> -                build_processor_hierarchy_node(
> -                    table_data,
> -                    (0 << 0), /* not a physical package */
> -                    parent_offset, cluster, NULL, 0);
> +        if (mc->smp_props.clusters_supported) {
> +            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;
> +                core_id = -1;
> +                cluster_offset = table_data->len - pptt_start;
> +                build_processor_hierarchy_node(table_data,
> +                    (0 << 0), /* Not a physical package */
> +                    socket_offset, cluster_id, NULL, 0);
>               }
> +        } else {
> +            cluster_offset = socket_offset;
>           }
> -    }
>   
> -    length = g_queue_get_length(list);
> -    for (i = 0; i < length; i++) {
> -        int core;
> -
> -        parent_offset = GPOINTER_TO_UINT(g_queue_pop_head(list));
> -        for (core = 0; core < ms->smp.cores; core++) {
> -            if (ms->smp.threads > 1) {
> -                g_queue_push_tail(list,
> -                    GUINT_TO_POINTER(table_data->len - pptt_start));
> -                build_processor_hierarchy_node(
> -                    table_data,
> +        if (ms->smp.threads == 1) {
> +            build_processor_hierarchy_node(table_data,
> +                (1 << 1) | /* ACPI Processor ID valid */
> +                (1 << 3),  /* Node is a Leaf */
> +                cluster_offset, n, NULL, 0);
> +        } else {
> +            if (cpus->cpus[n].props.core_id != core_id) {
> +                assert(cpus->cpus[n].props.core_id > core_id);
> +                core_id = cpus->cpus[n].props.core_id;
> +                core_offset = table_data->len - pptt_start;
> +                build_processor_hierarchy_node(table_data,
>                       (0 << 0), /* not a physical package */
nit: For consistency, maybe "Not a physical package"
> -                    parent_offset, core, NULL, 0);
> -            } else {
> -                build_processor_hierarchy_node(
> -                    table_data,
> -                    (1 << 1) | /* ACPI Processor ID valid */
> -                    (1 << 3),  /* Node is a Leaf */
> -                    parent_offset, uid++, NULL, 0);
> +                    cluster_offset, core_id, NULL, 0);
>               }
> -        }
> -    }
> -
> -    length = g_queue_get_length(list);
> -    for (i = 0; i < length; i++) {
> -        int thread;
>   
> -        parent_offset = GPOINTER_TO_UINT(g_queue_pop_head(list));
> -        for (thread = 0; thread < ms->smp.threads; thread++) {
> -            build_processor_hierarchy_node(
> -                table_data,
> +            build_processor_hierarchy_node(table_data,
>                   (1 << 1) | /* ACPI Processor ID valid */
>                   (1 << 2) | /* Processor is a Thread */
>                   (1 << 3),  /* Node is a Leaf */
> -                parent_offset, uid++, NULL, 0);
> +                core_offset, n, NULL, 0);
>           }
>       }
>   
> -    g_queue_free(list);
>       acpi_table_end(linker, &table);
>   }
>   
For the function of exposing vCPU topology to guest:
Tested-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Yanan Wang <wangyanan55@huawei.com>

Thanks,
Yanan