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

Markus Armbruster
2024-06-03T12:19:11Z

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:
> # …