[RFC PATCH v2 0/6] hw/arm/virt: Introduce cpu topology support

[Yanan Wang <wangyanan55@huawei.com>]

Hi,

This series is a new version of [0] recently posted by Ying Fang
to introduce cpu topology support for ARM platform. I have taken
over his work about this now, thanks for his contribution.

Description:
An accurate cpu topology may help improve the cpu scheduler's decision
making when dealing with multi-core system. So cpu topology description
is helpful to provide guest with the right view. Dario Faggioli's talk
in [1] also shows the virtual topology could have impact on scheduling
performace. Thus this patch series introduces cpu topology support for
ARM platform.

This series originally comes from Andrew Jones's patches [2], but with
some re-arrangement. Thanks for Andrew's contribution. In this series,
both fdt and ACPI PPTT table are introduced to present cpu topology to
the guest. And a new function virt_smp_parse() not like the default
smp_parse() is introduced, which prefers cores over sockets.

[0] https://patchwork.kernel.org/project/qemu-devel/cover/20210225085627.2263-1-fangying1@huawei.com/
[1] https://kvmforum2020.sched.com/event/eE1y/virtual-topology-for-virtual-machines-friend-or-foe-dario-faggioli-suse
[2] https://github.com/rhdrjones/qemu/commit/ecfc1565f22187d2c715a99bbcd35cf3a7e428fa

Test results:
After applying this patch series, launch a guest with virt-6.0 and cpu
topology configured with: -smp 96,sockets=2,clusters=6,cores=4,threads=2,
VM's cpu topology description shows as below.

Architecture:        aarch64
Byte Order:          Little Endian
CPU(s):              96
On-line CPU(s) list: 0-95
Thread(s) per core:  2
Core(s) per socket:  24
Socket(s):           2
NUMA node(s):        1
Vendor ID:           0x48
Model:               0
Stepping:            0x1
BogoMIPS:            200.00
NUMA node0 CPU(s):   0-95

---

Changelogs:
v1->v2:
- Address Andrew Jones's comments
- Address Michael S. Tsirkin's comments
- Pick up one more patch(patch#6) of Andrew Jones
- Rebased on v6.0.0-rc2 release

---

Andrew Jones (3):
  device_tree: Add qemu_fdt_add_path
  hw/arm/virt: DT: Add cpu-map
  hw/arm/virt: Replace smp_parse with one that prefers cores

Yanan Wang (2):
  hw/acpi/aml-build: Add processor hierarchy node structure
  hw/arm/virt-acpi-build: Add PPTT table

Ying Fang (1):
  hw/arm/virt-acpi-build: Distinguish possible and present cpus

 hw/acpi/aml-build.c          |  27 ++++++++
 hw/arm/virt-acpi-build.c     |  77 ++++++++++++++++++++--
 hw/arm/virt.c                | 120 ++++++++++++++++++++++++++++++++++-
 include/hw/acpi/aml-build.h  |   4 ++
 include/hw/arm/virt.h        |   1 +
 include/sysemu/device_tree.h |   1 +
 softmmu/device_tree.c        |  45 ++++++++++++-
 7 files changed, 268 insertions(+), 7 deletions(-)

-- 
2.19.1