Re: [PATCH 0/8] Introduce SMP Cache Topology

[Zhao Liu]

Hi Daniel and Markus,

A gentle ping. Would you kindly have a look at this version of the API
design? If it could meet your satisfaction, I’ll continue iterating.

Thanks,
Zhao

On Thu, Jul 04, 2024 at 11:15:55AM +0800, Zhao Liu wrote:
> Date: Thu, 4 Jul 2024 11:15:55 +0800
> From: Zhao Liu <zhao1.liu@intel.com>
> Subject: [PATCH 0/8] Introduce SMP Cache Topology
> X-Mailer: git-send-email 2.34.1
> 
> Hi all,
> 
> Since the previous RFC v2, I've reimplemented smp-cache object based on
> Daniel's comment (thanks Daniel!), which is both flexible to support
> current cache topology requirements and extensible.
> 
> So, I officially convert the RFC to PATCH.
> 
> Background on smp cache topology can be found in the previous RFC v2
> cover letter:
> 
> https://lore.kernel.org/qemu-devel/20240530101539.768484-1-zhao1.liu@intel.com/
> 
> The following content focuses on this series implementation of the
> smp-cache object.
> 
> 
> About smp-cache
> ===============
> 
> In fact, the smp-cache object introduced in this series is a bit
> different from Daniel's original suggestion. Instead of being integrated
> into -smp, it is created explicitly via -object, and the smp-cache
> property is added to -machine to link to this object.
> 
> An example is as follows:
> 
> -object 
> '{"qom-type":"smp-cache","id":"cache0","caches":[{"name":"l1d","topo":"core"},{"name":"l1i","topo":"core"},{"name":"l2","topo":"module"},{"name":"l3","topo":"socket"}]}'
> -machine smp-cache=cache0
> 
> 
> Such the design change is based on the following 2 reasons:
>  * Defining the cache with a JSON list is very extensible and can
>    support more cache properties.
> 
>  * But -smp, as the sugar of machine property "smp", is based on keyval
>    format, and doesn't support options with JSON format. Thus it's not
>    possible to add a JSON format based option to -smp/-machine for now.
> 
> So, I decoupled the creation of the smp-cache object from the -machine
> to make both -machine and -object happy!
> 
> 
> Welcome your feedback!
> 
> 
> Thanks and Best Regards,
> Zhao
> ---
> Changelog:
> 
> Main changes since RFC v2:
>  * Dropped cpu-topology.h and cpu-topology.c since QAPI has the helper
>    (CpuTopologyLevel_str) to convert enum to string. (Markus)
>  * Fixed text format in machine.json (CpuTopologyLevel naming, 2 spaces
>    between sentences). (Markus)
>  * Added a new level "default" to de-compatibilize some arch-specific
>    topo settings. (Daniel)
>  * Moved CpuTopologyLevel to qapi/machine-common.json, at where the
>    cache enumeration and smp-cache object would be added.
>    - If smp-cache object is defined in qapi/machine.json, storage-daemon
>      will complain about the qmp cmds in qapi/machine.json during
>      compiling.
>  * Referred to Daniel's suggestion to introduce cache JSON list, though
>    as a standalone object since -smp/-machine can't support JSON.
>  * Linked machine's smp_cache to smp-cache object instead of a builtin
>    structure. This is to get around the fact that the keyval format of
>    -machine can't support JSON.
>  * Wrapped the cache topology level access into a helper.
>  * Split as a separate commit to just include compatibility checking and
>    topology checking.
>  * Allow setting "default" topology level even though the cache
>    isn't supported by machine. (Daniel)
>  * Rewrote the document of smp-cache object.
> 
> Main changes since RFC v1:
>  * Split CpuTopology renaimg out of this RFC.
>  * Use QAPI to enumerate CPU topology levels.
>  * Drop string_to_cpu_topo() since QAPI will help to parse the topo
>    levels.
>  * Set has_*_cache field in machine_get_smp(). (JeeHeng)
>  * Use "*_cache=topo_level" as -smp example as the original "level"
>    term for a cache has a totally different meaning. (Jonathan)
> ---
> Zhao Liu (8):
>   hw/core: Make CPU topology enumeration arch-agnostic
>   qapi/qom: Introduce smp-cache object
>   hw/core: Add smp cache topology for machine
>   hw/core: Check smp cache topology support for machine
>   i386/cpu: Support thread and module level cache topology
>   i386/cpu: Update cache topology with machine's configuration
>   i386/pc: Support cache topology in -machine for PC machine
>   qemu-options: Add the description of smp-cache object
> 
>  MAINTAINERS                 |   2 +
>  hw/core/machine-smp.c       |  86 ++++++++++++++++++++++++++++++
>  hw/core/machine.c           |  22 ++++++++
>  hw/core/meson.build         |   1 +
>  hw/core/smp-cache.c         | 103 ++++++++++++++++++++++++++++++++++++
>  hw/i386/pc.c                |   4 ++
>  include/hw/boards.h         |  11 +++-
>  include/hw/core/smp-cache.h |  27 ++++++++++
>  include/hw/i386/topology.h  |  18 +------
>  qapi/machine-common.json    |  97 ++++++++++++++++++++++++++++++++-
>  qapi/qapi-schema.json       |   4 +-
>  qapi/qom.json               |   3 ++
>  qemu-options.hx             |  58 ++++++++++++++++++++
>  target/i386/cpu.c           |  83 +++++++++++++++++++++--------
>  target/i386/cpu.h           |   4 +-
>  15 files changed, 478 insertions(+), 45 deletions(-)
>  create mode 100644 hw/core/smp-cache.c
>  create mode 100644 include/hw/core/smp-cache.h
> 
> -- 
> 2.34.1
>