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Re: [PATCH for-6.2 v2 00/11] machine: smp parsing fixes and improvement

From: wangyanan (Y)
Subject: Re: [PATCH for-6.2 v2 00/11] machine: smp parsing fixes and improvement
Date: Wed, 21 Jul 2021 20:38:03 +0800
User-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0

On 2021/7/20 0:57, Cornelia Huck wrote:
On Mon, Jul 19 2021, Yanan Wang <wangyanan55@huawei.com> wrote:


This is v2 of the series [1] that I have posted to introduce some smp parsing
fixes and improvement, much more work has been processed compared to RFC v1.

[1] https://lists.gnu.org/archive/html/qemu-devel/2021-07/msg00259.html

The purpose of this series is to improve/fix the parsing logic. Explicitly
specifying a CPU topology parameter as zero is not allowed any more, and
maxcpus is now uniformly used to calculate the omitted parameters. 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.

In order to reduce code duplication and ease the code maintenance, smp_parse
in now converted into a parser generic enough for all arches, so that the PC
specific one can be removed. It's also convenient to introduce more topology
members (e.g. cluster) to the generic parser in the future.
Cc:ing Pierre, as he also had been looking at the smp parsing code (for
s390x) recently.

Also, please keep me on cc: for patches that touch s390x.
Sure, I will. Sorry about the missing. :)

Finally, a QEMU unit test for the parsing of given SMP configuration is added.
Since all the parsing logic is in generic function smp_parse(), this test
passes diffenent SMP configurations to the function and compare the parsing
result with what is expected. In the test, all possible collections of the
topology parameters and the corressponding 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 multi-dies are
also taken into consideration.



- 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)


Yanan Wang (11):
   machine: Disallow specifying topology parameters as zero
   machine: Make smp_parse generic enough for all arches
   machine: Uniformly use maxcpus to calculate the omitted parameters
   machine: Use the computed parameters to calculate omitted cpus
   machine: Improve the error reporting of smp parsing
   hw: Add compat machines for 6.2
   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: Split out the smp parsing code
   tests/unit: Add a unit test for smp parsing

  MAINTAINERS                 |    2 +
  hw/arm/virt.c               |   10 +-
  hw/core/machine-smp.c       |  124 ++++
  hw/core/machine.c           |   68 +--
  hw/core/meson.build         |    1 +
  hw/i386/pc.c                |   66 +--
  hw/i386/pc_piix.c           |   15 +-
  hw/i386/pc_q35.c            |   14 +-
  hw/ppc/spapr.c              |   16 +-
  hw/s390x/s390-virtio-ccw.c  |   15 +-
  include/hw/boards.h         |   13 +-
  include/hw/i386/pc.h        |    3 +
  qapi/machine.json           |    6 +-
  qemu-options.hx             |    4 +-
  tests/unit/meson.build      |    1 +
  tests/unit/test-smp-parse.c | 1117 +++++++++++++++++++++++++++++++++++
  16 files changed, 1338 insertions(+), 137 deletions(-)
  create mode 100644 hw/core/machine-smp.c
  create mode 100644 tests/unit/test-smp-parse.c


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