On Sun, Sep 08, 2024 at 08:59:13PM +0800, Zhao Liu wrote:
> Hi all,
>
> Compared with previous Patch v1 [1], I've put the cache properties list
> into -machine, this is to meet current needs and also remain compatible
> with my future topology support (more discussion details, pls refer [2]).
>
> This series is based on the commit 1581a0bc928d ("Merge tag 'pull-ufs-
> 20240906' of https://gitlab.com/jeuk20.kim/qemu into staging ufs
> queue").
Needs review from QOM maintainers.
> Background
> ==========
>
> The x86 and ARM (RISCV) need to allow user to configure cache properties
> (current only topology):
> * For x86, the default cache topology model (of max/host CPU) does not
> always match the Host's real physical cache topology. Performance can
> increase when the configured virtual topology is closer to the
> physical topology than a default topology would be.
> * For ARM, QEMU can't get the cache topology information from the CPU
> registers, then user configuration is necessary. Additionally, the
> cache information is also needed for MPAM emulation (for TCG) to
> build the right PPTT. (Originally from Jonathan)
>
>
> About smp-cache
> ===============
>
> In this version, smp-cache is implemented as a array integrated in
> -machine. Though -machine currently can't support JSON format, this is
> the one of the directions of future.
>
> An example is as follows:
>
> smp_cache=smp-cache.0.cache=l1i,smp-cache.0.topology=core,smp-cache.1.cache=l1d,smp-cache.1.topology=core,smp-cache.2.cache=l2,smp-cache.2.topology=module,smp-cache.3.cache=l3,smp-cache.3.topology=die
>
> "cache" specifies the cache that the properties will be applied on. This
> field is the combination of cache level and cache type. Now it supports
> "l1d" (L1 data cache), "l1i" (L1 instruction cache), "l2" (L2 unified
> cache) and "l3" (L3 unified cache).
>
> "topology" field accepts CPU topology levels including "thread", "core",
> "module", "cluster", "die", "socket", "book", "drawer" and a special
> value "default".
>
> The "default" is introduced to make it easier for libvirt to set a
> default parameter value without having to care about the specific
> machine (because currently there is no proper way for machine to
> expose supported topology levels and caches).
>
> If "default" is set, then the cache topology will follow the
> architecture's default cache topology model. If other CPU topology level
> is set, the cache will be shared at corresponding CPU topology level.
>
>
> Welcome your comment!
>
>
> [1]: Patch v1: https://lore.kernel.org/qemu-devel/20240704031603.1744546-1-zhao1.liu@xxxxxxxxx/
> [2]: API disscussion: https://lore.kernel.org/qemu-devel/8734ndj33j.fsf@xxxxxxxxxxxx/
>
> Thanks and Best Regards,
> Zhao
> ---
> Changelog:
>
> Main changes since Patch v1:
> * Dropped handwriten smp-cache object and integrated cache properties
> list into MachineState and used -machine to configure SMP cache
> properties. (Markus)
> * Dropped prefix of CpuTopologyLevel enumeration. (Markus)
> * Rename CPU_TOPO_LEVEL_* to CPU_TOPOLOGY_LEVEL_* to match the QAPI's
> generated code. (Markus)
> * Renamed SMPCacheProperty/SMPCacheProperties (QAPI structures) to
> SmpCacheProperties/SmpCachePropertiesWrapper. (Markus)
> * Renamed SMPCacheName (QAPI structure) to SmpCacheLevelAndType and
> dropped prefix. (Markus)
> * Renamed 'name' field in SmpCacheProperties to 'cache', since the
> type and level of the cache in SMP system could be able to specify
> all of these kinds of cache explicitly enough.
> * Renamed 'topo' field in SmpCacheProperties to 'topology'. (Markus)
> * Returned error information when user repeats setting cache
> properties. (Markus)
> * Renamed SmpCacheLevelAndType to CacheLevelAndType, since this
> representation is general across SMP or hybrid system.
> * Dropped machine_check_smp_cache_support() and did the check when
> -machine parses smp-cache in machine_parse_smp_cache().
>
> 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 (7):
> hw/core: Make CPU topology enumeration arch-agnostic
> qapi/qom: Define cache enumeration and properties
> 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
>
> hw/core/machine-smp.c | 119 +++++++++++++++++++++++
> hw/core/machine.c | 44 +++++++++
> hw/i386/pc.c | 4 +
> hw/i386/x86-common.c | 4 +-
> include/hw/boards.h | 13 +++
> include/hw/i386/topology.h | 22 +----
> qapi/machine-common.json | 96 ++++++++++++++++++-
> qemu-options.hx | 28 +++++-
> target/i386/cpu.c | 191 ++++++++++++++++++++++---------------
> target/i386/cpu.h | 4 +-
> 10 files changed, 425 insertions(+), 100 deletions(-)
>
> --
> 2.34.1
