Re: [RFC v2 1/7] hw/core: Make CPU topology enumeration arch-agnostic

[Markus Armbruster <armbru@redhat.com>]

Zhao Liu <zhao1.liu@intel.com> writes:

> Cache topology needs to be defined based on CPU topology levels. Thus,
> define CPU topology enumeration in qapi/machine.json to make it generic
> for all architectures.
>
> To match the general topology naming style, rename CPU_TOPO_LEVEL_SMT
> and CPU_TOPO_LEVEL_PACKAGE to CPU_TOPO_LEVEL_THREAD and
> CPU_TOPO_LEVEL_SOCKET.
>
> Also, enumerate additional topology levels for non-i386 arches, and add
> helpers for topology enumeration and string conversion.
>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
> Changes since RFC v1:
>  * Use QAPI to enumerate CPU topology levels.
>  * Drop string_to_cpu_topo() since QAPI will help to parse the topo
>    levels.
> ---
>  MAINTAINERS                    |  2 ++
>  hw/core/cpu-topology.c         | 36 ++++++++++++++++++++++++++++++
>  hw/core/meson.build            |  1 +
>  include/hw/core/cpu-topology.h | 20 +++++++++++++++++
>  include/hw/i386/topology.h     | 18 +--------------
>  qapi/machine.json              | 40 ++++++++++++++++++++++++++++++++++
>  target/i386/cpu.c              | 30 ++++++++++++-------------
>  target/i386/cpu.h              |  4 ++--
>  8 files changed, 117 insertions(+), 34 deletions(-)
>  create mode 100644 hw/core/cpu-topology.c
>  create mode 100644 include/hw/core/cpu-topology.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 448dc951c509..09173e8c953d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1875,6 +1875,7 @@ R: Yanan Wang <wangyanan55@huawei.com>
>  S: Supported
>  F: hw/core/cpu-common.c
>  F: hw/core/cpu-sysemu.c
> +F: hw/core/cpu-topology.c
>  F: hw/core/machine-qmp-cmds.c
>  F: hw/core/machine.c
>  F: hw/core/machine-smp.c
> @@ -1886,6 +1887,7 @@ F: qapi/machine-common.json
>  F: qapi/machine-target.json
>  F: include/hw/boards.h
>  F: include/hw/core/cpu.h
> +F: include/hw/core/cpu-topology.h
>  F: include/hw/cpu/cluster.h
>  F: include/sysemu/numa.h
>  F: tests/unit/test-smp-parse.c
> diff --git a/hw/core/cpu-topology.c b/hw/core/cpu-topology.c
> new file mode 100644
> index 000000000000..20b5d708cb54
> --- /dev/null
> +++ b/hw/core/cpu-topology.c
> @@ -0,0 +1,36 @@
> +/*
> + * QEMU CPU Topology Representation
> + *
> + * Copyright (c) 2024 Intel Corporation
> + *
> + * Authors:
> + *  Zhao Liu <zhao1.liu@intel.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later.  See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "hw/core/cpu-topology.h"
> +
> +typedef struct CPUTopoInfo {
> +    const char *name;
> +} CPUTopoInfo;
> +
> +CPUTopoInfo cpu_topo_descriptors[] = {
> +    [CPU_TOPO_LEVEL_INVALID] = { .name = "invalid", },
> +    [CPU_TOPO_LEVEL_THREAD]  = { .name = "thread",  },
> +    [CPU_TOPO_LEVEL_CORE]    = { .name = "core",    },
> +    [CPU_TOPO_LEVEL_MODULE]  = { .name = "module",  },
> +    [CPU_TOPO_LEVEL_CLUSTER] = { .name = "cluster", },
> +    [CPU_TOPO_LEVEL_DIE]     = { .name = "die",     },
> +    [CPU_TOPO_LEVEL_SOCKET]  = { .name = "socket",  },
> +    [CPU_TOPO_LEVEL_BOOK]    = { .name = "book",    },
> +    [CPU_TOPO_LEVEL_DRAWER]  = { .name = "drawer",  },
> +    [CPU_TOPO_LEVEL__MAX]    = { .name = NULL,      },
> +};

This looks redundant with generated

    const QEnumLookup CPUTopoLevel_lookup = {
        .array = (const char *const[]) {
            [CPU_TOPO_LEVEL_INVALID] = "invalid",
            [CPU_TOPO_LEVEL_THREAD] = "thread",
            [CPU_TOPO_LEVEL_CORE] = "core",
            [CPU_TOPO_LEVEL_MODULE] = "module",
            [CPU_TOPO_LEVEL_CLUSTER] = "cluster",
            [CPU_TOPO_LEVEL_DIE] = "die",
            [CPU_TOPO_LEVEL_SOCKET] = "socket",
            [CPU_TOPO_LEVEL_BOOK] = "book",
            [CPU_TOPO_LEVEL_DRAWER] = "drawer",
        },
        .size = CPU_TOPO_LEVEL__MAX
    };

> +
> +const char *cpu_topo_to_string(CPUTopoLevel topo)
> +{
> +    return cpu_topo_descriptors[topo].name;
> +}

And this with generated CPUTopoLevel_str().

> diff --git a/hw/core/meson.build b/hw/core/meson.build
> index a3d9bab9f42a..71dc396e9bfc 100644
> --- a/hw/core/meson.build
> +++ b/hw/core/meson.build
> @@ -13,6 +13,7 @@ hwcore_ss.add(files(
>  ))
>  
>  common_ss.add(files('cpu-common.c'))
> +common_ss.add(files('cpu-topology.c'))
>  common_ss.add(files('machine-smp.c'))
>  system_ss.add(when: 'CONFIG_FITLOADER', if_true: files('loader-fit.c'))
>  system_ss.add(when: 'CONFIG_GENERIC_LOADER', if_true: files('generic-loader.c'))
> diff --git a/include/hw/core/cpu-topology.h b/include/hw/core/cpu-topology.h
> new file mode 100644
> index 000000000000..0e21fe8a9bf8
> --- /dev/null
> +++ b/include/hw/core/cpu-topology.h
> @@ -0,0 +1,20 @@
> +/*
> + * QEMU CPU Topology Representation Header
> + *
> + * Copyright (c) 2024 Intel Corporation
> + *
> + * Authors:
> + *  Zhao Liu <zhao1.liu@intel.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later.  See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef CPU_TOPOLOGY_H
> +#define CPU_TOPOLOGY_H
> +
> +#include "qapi/qapi-types-machine.h"
> +
> +const char *cpu_topo_to_string(CPUTopoLevel topo);
> +
> +#endif /* CPU_TOPOLOGY_H */
> diff --git a/include/hw/i386/topology.h b/include/hw/i386/topology.h
> index dff49fce1154..c6ff75f23991 100644
> --- a/include/hw/i386/topology.h
> +++ b/include/hw/i386/topology.h
> @@ -39,7 +39,7 @@
>   *  CPUID Fn8000_0008_ECX[ApicIdCoreIdSize[3:0]] is set to apicid_core_width().
>   */
>  
> -
> +#include "hw/core/cpu-topology.h"
>  #include "qemu/bitops.h"
>  
>  /*
> @@ -62,22 +62,6 @@ typedef struct X86CPUTopoInfo {
>      unsigned threads_per_core;
>  } X86CPUTopoInfo;
>  
> -/*
> - * CPUTopoLevel is the general i386 topology hierarchical representation,
> - * ordered by increasing hierarchical relationship.
> - * Its enumeration value is not bound to the type value of Intel (CPUID[0x1F])
> - * or AMD (CPUID[0x80000026]).
> - */
> -enum CPUTopoLevel {
> -    CPU_TOPO_LEVEL_INVALID,
> -    CPU_TOPO_LEVEL_SMT,
> -    CPU_TOPO_LEVEL_CORE,
> -    CPU_TOPO_LEVEL_MODULE,
> -    CPU_TOPO_LEVEL_DIE,
> -    CPU_TOPO_LEVEL_PACKAGE,
> -    CPU_TOPO_LEVEL_MAX,
> -};
> -
>  /* Return the bit width needed for 'count' IDs */
>  static unsigned apicid_bitwidth_for_count(unsigned count)
>  {
> diff --git a/qapi/machine.json b/qapi/machine.json
> index bce6e1bbc412..7ac5a05bb9c9 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1667,6 +1667,46 @@
>       '*reboot-timeout': 'int',
>       '*strict': 'bool' } }
>  
> +##
> +# @CPUTopoLevel:
> +#
> +# An enumeration of CPU topology levels.
> +#
> +# @invalid: Invalid topology level, used as a placeholder.

Placeholder for what?

> +#
> +# @thread: thread level, which would also be called SMT level or logical
> +#     processor level. The @threads option in -smp is used to configure
> +#     the topology of this level.
> +#
> +# @core: core level. The @cores option in -smp is used to configure the
> +#     topology of this level.
> +#
> +# @module: module level. The @modules option in -smp is used to
> +#     configure the topology of this level.
> +#
> +# @cluster: cluster level. The @clusters option in -smp is used to
> +#     configure the topology of this level.
> +#
> +# @die: die level. The @dies option in -smp is used to configure the
> +#     topology of this level.
> +#
> +# @socket: socket level, which would also be called package level. The
> +#     @sockets option in -smp is used to configure the topology of this
> +#     level.
> +#
> +# @book: book level. The @books option in -smp is used to configure the
> +#     topology of this level.
> +#
> +# @drawer: drawer level. The @drawers option in -smp is used to
> +#     configure the topology of this level.

As far as I can tell, -smp is sugar for machine property "smp" of QAPI
type SMPConfiguration.  Should we refer to SMPConfiguration instead of
-smp?

> +#
> +# Since: 9.1
> +##
> +{ 'enum': 'CPUTopoLevel',
> +  'prefix': 'CPU_TOPO_LEVEL',
> +  'data': [ 'invalid', 'thread', 'core', 'module', 'cluster',
> +            'die', 'socket', 'book', 'drawer' ] }
> +
>  ##
>  # @SMPConfiguration:
>  #

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