Re: [PATCH v17 6/8] hw/acpi: add cache hierarchy to pptt table

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

On Tue, Jan 06, 2026 at 03:58:25PM +0000, Alireza Sanaee wrote:
> Add cache topology to PPTT table.
> 
> Signed-off-by: Alireza Sanaee <alireza.sanaee@huawei.com>
> ---
>  hw/acpi/aml-build.c      | 200 +++++++++++++++++++++++++++++++++++++--
>  hw/arm/virt-acpi-build.c |   8 +-
>  include/hw/acpi/cpu.h    |  10 ++
>  3 files changed, 209 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> index a711a9600e..580eceb24a 100644
> --- a/hw/acpi/aml-build.c
> +++ b/hw/acpi/aml-build.c
> @@ -31,6 +31,7 @@
>  #include "hw/pci/pci_bus.h"
>  #include "hw/pci/pci_bridge.h"
>  #include "qemu/cutils.h"
> +#include "hw/core/cpu.h"
>  
>  static GArray *build_alloc_array(void)
>  {
> @@ -2140,6 +2141,104 @@ void build_spcr(GArray *table_data, BIOSLinker *linker,
>      }
>      acpi_table_end(linker, &table);
>  }
> +
> +static void build_cache_nodes(GArray *tbl, CPUCoreCaches *cache,
> +                              uint32_t next_offset)
> +{
> +    int val;
> +
> +    /* Type 1 - cache */
> +    build_append_byte(tbl, 1);

Standard format in acpi code is:
    build_append_byte(tbl, 1); /* Type 1 - cache */

same below

> +    /* Length */
> +    build_append_byte(tbl, 24);

would be nice to validate. you can compare tbl->len before and after.


> +    /* Reserved */
> +    build_append_int_noprefix(tbl, 0, 2);
> +    /* Flags */
> +    build_append_int_noprefix(tbl, 0x7f, 4);

document which flags are set.


> +    /* Offset of next cache up */
> +    build_append_int_noprefix(tbl, next_offset, 4);
> +    build_append_int_noprefix(tbl, cache->size, 4);
> +    build_append_int_noprefix(tbl, cache->sets, 4);
> +    build_append_byte(tbl, cache->associativity);
> +    val = 0x3;

document what this is

> +    switch (cache->type) {
> +    case INSTRUCTION_CACHE:
> +        val |= (1 << 2);

document what this is.

> +        break;
> +    case DATA_CACHE:
> +        val |= (0 << 2); /* Data */
> +        break;
> +    case UNIFIED_CACHE:
> +        val |= (3 << 2); /* Unified */
> +        break;
> +    }
> +    build_append_byte(tbl, val);
> +    build_append_int_noprefix(tbl, cache->linesize, 2);
> +}
> +
> +/*
> + * builds caches from the top level (`level_high` parameter) to the bottom
> + * level (`level_low` parameter).  It searches for caches found in
> + * systems' registers, and fills up the table. Then it updates the
> + * `data_offset` and `instr_offset` parameters with the offset of the data
> + * and instruction caches of the lowest level, respectively.
> + */
> +static bool build_caches(GArray *table_data, uint32_t pptt_start,
> +                         int num_caches, CPUCoreCaches *caches,
> +                         uint8_t level_high, /* Inclusive */
> +                         uint8_t level_low,  /* Inclusive */
> +                         uint32_t *data_offset,
> +                         uint32_t *instr_offset)
> +{
> +    uint32_t next_level_offset_data = 0, next_level_offset_instruction = 0;
> +    uint32_t this_offset, next_offset = 0;
> +    int c, level;
> +    bool found_cache = false;
> +
> +    /* Walk caches from top to bottom */
> +    for (level = level_high; level >= level_low; level--) {
> +        for (c = 0; c < num_caches; c++) {
> +            if (caches[c].level != level) {
> +                continue;
> +            }
> +
> +            /* Assume only unified above l1 for now */
> +            this_offset = table_data->len - pptt_start;
> +            switch (caches[c].type) {
> +            case INSTRUCTION_CACHE:
> +                next_offset = next_level_offset_instruction;
> +                break;
> +            case DATA_CACHE:
> +                next_offset = next_level_offset_data;
> +                break;
> +            case UNIFIED_CACHE:
> +                /* Either is fine here */
> +                next_offset = next_level_offset_instruction;
> +                break;
> +            }
> +            build_cache_nodes(table_data, &caches[c], next_offset);
> +            switch (caches[c].type) {
> +            case INSTRUCTION_CACHE:
> +                next_level_offset_instruction = this_offset;
> +                break;
> +            case DATA_CACHE:
> +                next_level_offset_data = this_offset;
> +                break;
> +            case UNIFIED_CACHE:
> +                next_level_offset_instruction = this_offset;
> +                next_level_offset_data = this_offset;
> +                break;
> +            }
> +            *data_offset = next_level_offset_data;
> +            *instr_offset = next_level_offset_instruction;
> +
> +            found_cache = true;
> +        }
> +    }
> +
> +    return found_cache;
> +}
> +
>  /*
>   * ACPI spec, Revision 6.3
>   * 5.2.29 Processor Properties Topology Table (PPTT)
> @@ -2150,11 +2249,32 @@ void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
>  {
>      MachineClass *mc = MACHINE_GET_CLASS(ms);
>      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 core_data_offset = 0;
> +    uint32_t core_instr_offset = 0;
> +    uint32_t cluster_instr_offset = 0;
> +    uint32_t cluster_data_offset = 0;
> +    uint32_t node_data_offset = 0;
> +    uint32_t node_instr_offset = 0;
> +    int top_node = 3;
> +    int top_cluster = 3;
> +    int top_core = 3;
> +    int bottom_node = 3;
> +    int bottom_cluster = 3;
> +    int bottom_core = 3;
> +    int64_t socket_id = -1;
> +    int64_t cluster_id = -1;
> +    int64_t core_id = -1;
> +    uint32_t socket_offset = 0;
> +    uint32_t cluster_offset = 0;
> +    uint32_t core_offset = 0;
>      uint32_t pptt_start = table_data->len;
>      uint32_t root_offset;
>      int n;
> +    uint32_t priv_rsrc[2];
> +    uint32_t num_priv = 0;
> +    bool cache_available;
> +    bool llevel;
> +
>      AcpiTable table = { .sig = "PPTT", .rev = 2,
>                          .oem_id = oem_id, .oem_table_id = oem_table_id };
>  
> @@ -2184,11 +2304,30 @@ void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
>              socket_id = cpus->cpus[n].props.socket_id;
>              cluster_id = -1;
>              core_id = -1;
> +            bottom_node = top_node;
> +            num_priv = 0;
> +            cache_available = machine_defines_cache_at_topo_level(
> +                ms, CPU_TOPOLOGY_LEVEL_SOCKET);
> +            llevel = machine_find_lowest_level_cache_at_topo_level(
> +                ms, &bottom_node, CPU_TOPOLOGY_LEVEL_SOCKET);
> +            if (cache_available && llevel) {
> +                build_caches(table_data, pptt_start, num_caches, caches,
> +                             top_node, bottom_node, &node_data_offset,
> +                             &node_instr_offset);
> +                priv_rsrc[0] = node_instr_offset;
> +                priv_rsrc[1] = node_data_offset;
> +                if (node_instr_offset || node_data_offset) {
> +                    num_priv = node_instr_offset == node_data_offset ? 1 : 2;
> +                }
> +
> +                top_cluster = bottom_node - 1;
> +            }
> +
>              socket_offset = table_data->len - pptt_start;
>              build_processor_hierarchy_node(table_data,
>                  (1 << 0) | /* Physical package */
>                  (1 << 4), /* Identical Implementation */
> -                root_offset, socket_id, NULL, 0);
> +                root_offset, socket_id, priv_rsrc, num_priv);
>          }
>  
>          if (mc->smp_props.clusters_supported && mc->smp_props.has_clusters) {
> @@ -2196,21 +2335,68 @@ void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
>                  assert(cpus->cpus[n].props.cluster_id > cluster_id);
>                  cluster_id = cpus->cpus[n].props.cluster_id;
>                  core_id = -1;
> +                bottom_cluster = top_cluster;
> +                num_priv = 0;
> +                cache_available = machine_defines_cache_at_topo_level(
> +                    ms, CPU_TOPOLOGY_LEVEL_CLUSTER);
> +                llevel = machine_find_lowest_level_cache_at_topo_level(
> +                    ms, &bottom_cluster, CPU_TOPOLOGY_LEVEL_CLUSTER);
> +
> +                if (cache_available && llevel) {
> +                    build_caches(table_data, pptt_start, num_caches, caches,
> +                                 top_cluster, bottom_cluster,
> +                                 &cluster_data_offset, &cluster_instr_offset);
> +                    priv_rsrc[0] = cluster_instr_offset;
> +                    priv_rsrc[1] = cluster_data_offset;
> +                    if (cluster_instr_offset || cluster_data_offset) {
> +                        num_priv =
> +                            cluster_instr_offset == cluster_data_offset ? 1 : 2;
> +                    }
> +                    top_core = bottom_cluster - 1;
> +                } else if (top_cluster == bottom_node - 1) {
> +                    /* socket cache but no cluster cache */
> +                    top_core = bottom_node - 1;
> +                }
> +
>                  cluster_offset = table_data->len - pptt_start;
>                  build_processor_hierarchy_node(table_data,
>                      (0 << 0) | /* Not a physical package */
>                      (1 << 4), /* Identical Implementation */
> -                    socket_offset, cluster_id, NULL, 0);
> +                    socket_offset, cluster_id, priv_rsrc, num_priv);
>              }
>          } else {
> +            if (machine_defines_cache_at_topo_level(
> +                    ms, CPU_TOPOLOGY_LEVEL_CLUSTER)) {
> +                error_setg(&error_fatal, "Not clusters found for the cache");
> +                return;
> +            }
> +
>              cluster_offset = socket_offset;
> +            top_core = bottom_node - 1; /* there is no cluster */
> +        }
> +
> +        if (cpus->cpus[n].props.core_id != core_id) {
> +            bottom_core = top_core;
> +            num_priv = 0;
> +            cache_available = machine_defines_cache_at_topo_level(
> +                ms, CPU_TOPOLOGY_LEVEL_CORE);
> +            llevel = machine_find_lowest_level_cache_at_topo_level(
> +                ms, &bottom_core, CPU_TOPOLOGY_LEVEL_CORE);
> +            if (cache_available && llevel) {
> +                build_caches(table_data, pptt_start, num_caches, caches,
> +                             top_core, bottom_core, &core_data_offset,
> +                             &core_instr_offset);
> +                priv_rsrc[0] = core_instr_offset;
> +                priv_rsrc[1] = core_data_offset;
> +                num_priv = core_instr_offset == core_data_offset ? 1 : 2;
> +            }
>          }
>  
>          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);
> +                (1 << 3), /* Node is a Leaf */
> +                cluster_offset, n, priv_rsrc, num_priv);
>          } else {
>              if (cpus->cpus[n].props.core_id != core_id) {
>                  assert(cpus->cpus[n].props.core_id > core_id);
> @@ -2219,7 +2405,7 @@ void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
>                  build_processor_hierarchy_node(table_data,
>                      (0 << 0) | /* Not a physical package */
>                      (1 << 4), /* Identical Implementation */
> -                    cluster_offset, core_id, NULL, 0);
> +                    cluster_offset, core_id, priv_rsrc, num_priv);
>              }
>  
>              build_processor_hierarchy_node(table_data,
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 8e7bc029f3..f4cbb71c90 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -1144,6 +1144,10 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
>      unsigned dsdt, xsdt;
>      GArray *tables_blob = tables->table_data;
>      MachineState *ms = MACHINE(vms);
> +    CPUCoreCaches caches[CPU_MAX_CACHES];
> +    unsigned int num_caches;
> +
> +    num_caches = virt_get_caches(vms, caches);
>  
>      table_offsets = g_array_new(false, true /* clear */,
>                                          sizeof(uint32_t));
> @@ -1165,8 +1169,8 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
>  
>      if (!vmc->no_cpu_topology) {
>          acpi_add_table(table_offsets, tables_blob);
> -        build_pptt(tables_blob, tables->linker, ms,
> -                   vms->oem_id, vms->oem_table_id, 0, NULL);
> +        build_pptt(tables_blob, tables->linker, ms, vms->oem_id,
> +                   vms->oem_table_id, num_caches, caches);
>      }
>  
>      acpi_add_table(table_offsets, tables_blob);
> diff --git a/include/hw/acpi/cpu.h b/include/hw/acpi/cpu.h
> index 557219d2c6..87950eb787 100644
> --- a/include/hw/acpi/cpu.h
> +++ b/include/hw/acpi/cpu.h
> @@ -70,6 +70,16 @@ void build_cpus_aml(Aml *table, MachineState *machine, CPUHotplugFeatures opts,
>  
>  void acpi_cpu_ospm_status(CPUHotplugState *cpu_st, ACPIOSTInfoList ***list);
>  
> +struct CPUPPTTCaches {
> +    enum CacheType type;
> +    uint32_t sets;
> +    uint32_t size;
> +    uint32_t level;
> +    uint16_t linesize;
> +    uint8_t attributes; /* write policy: 0x0 write back, 0x1 write through */
> +    uint8_t associativity;
> +};
> +
>  extern const VMStateDescription vmstate_cpu_hotplug;
>  #define VMSTATE_CPU_HOTPLUG(cpuhp, state) \
>      VMSTATE_STRUCT(cpuhp, state, 1, \
> -- 
> 2.43.0