tree f00ddc313f57afb9128d787f34f08157a6588b84
parent 33956e476802a6ae9b9a8e047f6a78e09e9ae180
author Maksim Davydov <davydov-max@yandex-team.ru> 1710797750 +0300
committer Philippe Mathieu-Daudé <philmd@linaro.org> 1714032768 +0200

scripts: add script to compare compatibility properties

This script runs QEMU to obtain compat_props of machines and default
values of different types of drivers to produce comparison table. This
table can be used to compare machine types to choose the most suitable
machine or compare binaries to be sure that migration to the newer version
will save all device properties. Also the json or csv format of this
table can be used to check does a new machine affect the previous ones by
comparing tables with and without the new machine.

Default values (that will be used without machine compat_props) of
properties are needed to fill "holes" in the table (one machine has
the property but another machine not. For instance, 2.12 machine has
`{ "EPYC-" TYPE_X86_CPU, "xlevel", "0x8000000a" }`, but compat_pros of
3.1 machine doesn't have it. Thus, to compare these machines we need to
get unknown value of "EPYC-x86_64-cpu-xlevel" for 3.1 machine. These
unknown values in the table are called "holes". To get values for these
"holes" the script uses list of appropriate methods.)

Notes:
* Some init values from the devices can't be available like properties
  from virtio-9p when configure has --disable-virtfs. This situations will
  be seen in the table as "unavailable driver".
* Default values can be obtained in an unobvious way, like x86 features.
  If the script doesn't know how to get property default value to compare
  one machine with another it fills "holes" with "unavailable method". This
  is done because script uses whitelist model to get default values of
  different types. It means that the method that can't be applied to a new
  type that can crash this script. It is better to get an "unavailable
  driver" when creating a new machine with new compatible properties than
  to break this script. So it turns out a more stable and generic script.
* If the default value can't be obtained because this property doesn't
  exist or because this property can't have default value, appropriate
  "hole" will be filled by "unknown property" or "no default value"
* If the property is applied to the abstract class, the script collects
  default values from all child classes and prints all these classes
* Raw table (--raw flag) should be used with json/csv parameters for
  scripts and etc. Human-readable (default) format contains transformed
  and simplified values and it doesn't contain lines with the same values
  in columns

Example:
./scripts/compare-machine-types.py --mt pc-q35-6.2 pc-q35-7.1
╒══════════════════╤══════════════════════════╤════════════════════════════╤════════════════════════════╕
│      Driver      │         Property         │  build/qemu-system-x86_64  │  build/qemu-system-x86_64  │
│                  │                          │         pc-q35-6.2         │         pc-q35-7.1         │
╞══════════════════╪══════════════════════════╪════════════════════════════╪════════════════════════════╡
│     PIIX4_PM     │ x-not-migrate-acpi-index │            True            │           False            │
├──────────────────┼──────────────────────────┼────────────────────────────┼────────────────────────────┤
│ arm-gicv3-common │     force-8-bit-prio     │            True            │     unavailable driver     │
├──────────────────┼──────────────────────────┼────────────────────────────┼────────────────────────────┤
│     nvme-ns      │      eui64-default       │            True            │           False            │
├──────────────────┼──────────────────────────┼────────────────────────────┼────────────────────────────┤
│    virtio-mem    │  unplugged-inaccessible  │           False            │            auto            │
╘══════════════════╧══════════════════════════╧════════════════════════════╧════════════════════════════╛

Signed-off-by: Maksim Davydov <davydov-max@yandex-team.ru>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20240318213550.155573-5-davydov-max@yandex-team.ru>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>