Re: [PATCH v4 0/9] Introduce SMP Cache Topology

Zhao Liu
2024-10-28T08:51:32Z

Kindly Ping.

(Hi miantainers, all the patches have received Jonathan's review. Could
this series be accepted?)

Thanks,
Zhao

On Tue, Oct 22, 2024 at 09:51:42PM +0800, Zhao Liu wrote:
> Date: Tue, 22 Oct 2024 21:51:42 +0800
> From: Zhao Liu <zhao1.liu@intel.com>
> Subject: [PATCH v4 0/9] Introduce SMP Cache Topology
> X-Mailer: git-send-email 2.34.1
>
> Hi all,
>
> Compared with v3 [1], the v4 mainly changes these places:
>
> * Don't expose "invalid" enumeration in QAPI and define it by a
> macro instead. (new patch 1, and updated patch 2)
>
> * Check cache topology after the arch machine loads the user-
> configured cache model from MachineState.smp_cache and consumes
> the special "default" level by replacing it with the specific level.
> (new patch 5, and updated patch 7)
>
> * Describ the omitting cache will use "default" level and describ
> the default cache topology model of i386 PC machine. (updated
> patch 8)
>
> All the above changes are tested and the interface design has remained
> stable.
>
> Meanwhile, ARM side has also worked a lot on the smp-cache based on
> this series [2].
>
> This series is based on the commit cc5adbbd50d8 ("Merge tag
> 'pull-tpm-2024-10-18-1' of https://github.com/stefanberger/qemu-tpm into
> staging").
>
> Welcome your feedback, and I appreciate your reviews. Hope our series
> can catch up with the 9.2 cycle. :)
>
>
> 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
> ===============
>
> The API design has been discussed heavily in [3].
>
> Now, 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 feedback and review!
>
> [1]: Patch v3: https://lore.kernel.org/qemu-devel/20241012104429.1048908-1-zhao1.liu@intel.com/
> [2]: ARM smp-cache: https://lore.kernel.org/qemu-devel/20241010111822.345-1-alireza.sanaee@huawei.com/
> [3]: API disscussion: https://lore.kernel.org/qemu-devel/8734ndj33j.fsf@pond.sub.org/
>
> Thanks and Best Regards,
> Zhao
> ---
> Changelog:
>
> Main changes since Patch v3:
> * Stopped exposing "invalid" enumeration in QAPI and define it by a
> macro instead. (Dainel)
> * Checked cache topology after the arch machine loads the
> user-configured cache model from MachineState.smp_cache and consumes
> the special "default" level by replacing it with the specific level.
> (Daniel)
> * Described the omitting cache will use "default" level and described
> the default cache topology model of i386 PC machine. (Daniel)
>
> Main changes since Patch v2:
> * Updated version of new QAPI structures to v9.2. (Jonathan)
> * Merged the QAPI change and smp-cache property support of machine
> into one commit. (Jonathan)
> * Picked Alireza's patch to add a has_caches flag.
> * Polished english and coding style. (Jonathan)
>
> 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)
> ---
> Alireza Sanaee (1):
> i386/cpu: add has_caches flag to check smp_cache configuration
>
> Zhao Liu (8):
> i386/cpu: Don't enumerate the "invalid" CPU topology level
> hw/core: Make CPU topology enumeration arch-agnostic
> qapi/qom: Define cache enumeration and properties for machine
> hw/core: Check smp cache topology support for machine
> hw/core: Add a helper to check the cache topology level
> 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 | 128 +++++++++++++++++++++
> hw/core/machine.c | 44 ++++++++
> hw/i386/pc.c | 4 +
> hw/i386/x86-common.c | 4 +-
> include/hw/boards.h | 19 ++++
> include/hw/i386/topology.h | 22 +---
> qapi/machine-common.json | 94 +++++++++++++++-
> qemu-options.hx | 31 ++++-
> target/i386/cpu.c | 225 ++++++++++++++++++++++++-------------
> target/i386/cpu.h | 4 +-
> 10 files changed, 474 insertions(+), 101 deletions(-)
>
> --
> 2.34.1
>
>