[PATCH v8 00/14] machine: smp parsing fixes and improvement

[Yanan Wang]

I'm resending a new version, as one patch (hw: Add compat machines for 6.2)
of the series has been merged into upstream. There are no changes of the
other patches since v7 though. Series has been fully reviewed.

Description:
This series introduces some fixes and improvement for the SMP parsing.

1) Specifying a CPU topology parameter as zero was implicitly allowed
but undocumented before, while now it's explicitly deprecated.

2) To keep consistency, maxcpus is now uniformly used to calculate the
omitted topology members.

3) Improve the error reporting.

4) It's also suggested that we should start to prefer cores over sockets
over threads on the newer machine types, which will make the computed
virtual topology more reflective of the real hardware. Related discussion
can be found in [1].
[1] https://lore.kernel.org/qemu-devel/YNIgInK00yNNI4Dy@redhat.com/

5) In order to reduce code duplication and ease the code maintenance,
smp_parse() is converted into a generic enough parser for all arches,
so that the arch-specific ones (e.g. pc_smp_parse) can be removed.
It's also convenient to introduce more topology members to the generic
parser in the future. Related discussions can be found in [2] and [3].
[2] 
https://lore.kernel.org/qemu-devel/20210630115602.txmvmfe2jrzu7o67@gator.home/
[3] https://lore.kernel.org/qemu-devel/YPFN83pKBt7F97kW@redhat.com/

6) A unit test for the SMP parsing is added. In the test, all possible
collections of the topology parameters and the corresponding expected
results are listed, including the valid and invalid ones. The preference
of sockets over cores and the preference of cores over sockets, and the
support of dies are also taken into consideration.

---

Changelogs:

v7->v8:
- merge patch (hw: Add compat machines for 6.2) separately
- rebased on upstream commit 079b1252e9
- v7: 
https://lore.kernel.org/qemu-devel/20210823122804.7692-1-wangyanan55@huawei.com/

v6->v7:
- drop the two docs/about clean-up patches and they have been resent separately
- v6: 
https://lore.kernel.org/qemu-devel/20210819031027.41104-1-wangyanan55@huawei.com/

v5->v6:
- deprecate "parameter=0" SMP configurations (patch #1 and #2 added)
- rebased on upstream v6.1.0-rc4
- v5: 
https://lore.kernel.org/qemu-devel/20210813023912.105880-1-wangyanan55@huawei.com/

v4->v5:
- refactor out the duplicated "threads == 0" case in patch #6 (Pankaj)
- pick up more R-b tags from v4 (thanks very much for the review!)
- v4: 
https://lore.kernel.org/qemu-devel/20210803080527.156556-1-wangyanan55@huawei.com/

v3->v4:
- put all the sanity check into the parser
- refine the unit test and add it back to the series
- add the R-b/A-b tags for the reviewed/acked patches
- v3: 
https://lore.kernel.org/qemu-devel/20210728034848.75228-1-wangyanan55@huawei.com/

v2->v3:
- apply the calculation improvement to smp_parse and pc_smp_parse
  separately and then convert the finally improved parsers into a
  generic one, so that patches can be reviewed separately.
- to ease review, drop the unit test part for a while until we have
  a good enough generic parser.
- send the patch "machine: Disallow specifying topology parameters as zero"
  for 6.1 separately.
- v2: 
https://lore.kernel.org/qemu-devel/20210719032043.25416-1-wangyanan55@huawei.com/

v1->v2:
- disallow "anything=0" in the smp configuration (Andrew)
- make function smp_parse() a generic helper for all arches
- improve the error reporting in the parser
- start to prefer cores over sockets since 6.2 (Daniel)
- add a unit test for the smp parsing (Daniel)
- v1: 
https://lore.kernel.org/qemu-devel/20210702100739.13672-1-wangyanan55@huawei.com/

---

Yanan Wang (14):
  machine: Deprecate "parameter=0" SMP configurations
  machine: Minor refactor/fix for the smp parsers
  machine: Uniformly use maxcpus to calculate the omitted parameters
  machine: Set the value of cpus to match maxcpus if it's omitted
  machine: Improve the error reporting of smp parsing
  machine: Prefer cores over sockets in smp parsing since 6.2
  machine: Use ms instead of global current_machine in sanity-check
  machine: Tweak the order of topology members in struct CpuTopology
  machine: Make smp_parse generic enough for all arches
  machine: Remove smp_parse callback from MachineClass
  machine: Move smp_prefer_sockets to struct SMPCompatProps
  machine: Put all sanity-check in the generic SMP parser
  machine: Split out the smp parsing code
  tests/unit: Add a unit test for smp parsing

 MAINTAINERS                 |   2 +
 docs/about/deprecated.rst   |  15 +
 hw/arm/virt.c               |   1 +
 hw/core/machine-smp.c       | 200 +++++++++
 hw/core/machine.c           |  90 +---
 hw/core/meson.build         |   1 +
 hw/i386/pc.c                |  63 +--
 hw/i386/pc_piix.c           |   1 +
 hw/i386/pc_q35.c            |   1 +
 hw/ppc/spapr.c              |   1 +
 hw/s390x/s390-virtio-ccw.c  |   1 +
 include/hw/boards.h         |  24 +-
 qapi/machine.json           |   2 +-
 qemu-options.hx             |  24 +-
 tests/unit/meson.build      |   1 +
 tests/unit/test-smp-parse.c | 866 ++++++++++++++++++++++++++++++++++++
 16 files changed, 1130 insertions(+), 163 deletions(-)
 create mode 100644 hw/core/machine-smp.c
 create mode 100644 tests/unit/test-smp-parse.c

--
2.19.1