[RFC] kunit: tool: Enable virtio/PCI by default on UML

There are several tests which depend on PCI, and hence need a bunch of
extra options to run under UML. This makes it awkward to give
configuration instructions (whether in documentation, or as part of a
.kunitconfig file), as two separate, incompatible sets of config options
are required for UML and "most other architectures".

For non-UML architectures, it's possible to add default kconfig options
via the qemu_config python files, but there's no equivalent for UML. Add
a new tools/testing/kunit/configs/arch_uml.config file containing extra
kconfig options to use on UML.

Signed-off-by: David Gow <davidgow@google.com>
---

It's really ugly to have to type:
	--kconfig_add CONFIG_VIRTIO_UML=y
	--kconfig_add CONFIG_UML_PCI_OVER_VIRTIO=y
when running many tests under UML, particularly since it isn't required
on other architectures.

This came up in discussion with Daniel this morning, and while the
ability to repeat the --kunitconfig flag would go some way to alleviate
this, having to add:
	--kunitconfig ./tools/testing/kunit/config/uml_pci.kunitconfig
isn't all that much better.

So it seems like adding something by default would be nice.

This implementation is not perfect (in particular, there's no easy way
of _disabling_ these options now, though [1] probably will help). The
'arch_uml.config' filename can be bikeshedded, too.

Thoughts?

---
 tools/testing/kunit/configs/arch_uml.config |  5 +++++
 tools/testing/kunit/kunit_kernel.py         | 11 ++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/kunit/configs/arch_uml.config

On Tue, Jun 21, 2022 at 8:53 PM David Gow <davidgow@google.com> wrote:
>
> There are several tests which depend on PCI, and hence need a bunch of
> extra options to run under UML. This makes it awkward to give
> configuration instructions (whether in documentation, or as part of a
> .kunitconfig file), as two separate, incompatible sets of config options
> are required for UML and "most other architectures".
>
> For non-UML architectures, it's possible to add default kconfig options
> via the qemu_config python files, but there's no equivalent for UML. Add
> a new tools/testing/kunit/configs/arch_uml.config file containing extra
> kconfig options to use on UML.
>
> Signed-off-by: David Gow <davidgow@google.com>
> ---
>
> It's really ugly to have to type:
>         --kconfig_add CONFIG_VIRTIO_UML=y
>         --kconfig_add CONFIG_UML_PCI_OVER_VIRTIO=y
> when running many tests under UML, particularly since it isn't required
> on other architectures.
>
> This came up in discussion with Daniel this morning, and while the
> ability to repeat the --kunitconfig flag would go some way to alleviate
> this, having to add:
>         --kunitconfig ./tools/testing/kunit/config/uml_pci.kunitconfig
> isn't all that much better.
>
> So it seems like adding something by default would be nice.
>
> This implementation is not perfect (in particular, there's no easy way
> of _disabling_ these options now, though [1] probably will help). The
> 'arch_uml.config' filename can be bikeshedded, too.
>
> Thoughts?

I am supportive of adding the PCI dependency as a default for UML; I
agree that there is a common desire to use PCI for tests and enabling
it on UML is wonky.

One additional note: It looks like this patch breaks kunit_tool:
https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/21871

The python error in the log seems legitimate:
https://storage.googleapis.com/oss-prow/pr-logs/pull/linux-review.googlesource.com_linux_kernel_git_torvalds_linux/21871/linux-kernel-mailing-list-presubmit/1539456886976286720/build-log.txt

This line in particular:

AttributeError: 'LinuxSourceTreeOperationsUml' object has no attribute
'make_arch_qemuconfig'

> ---
>  tools/testing/kunit/configs/arch_uml.config |  5 +++++
>  tools/testing/kunit/kunit_kernel.py         | 11 ++++++++---
>  2 files changed, 13 insertions(+), 3 deletions(-)
>  create mode 100644 tools/testing/kunit/configs/arch_uml.config
>
> diff --git a/tools/testing/kunit/configs/arch_uml.config b/tools/testing/kunit/configs/arch_uml.config
> new file mode 100644
> index 000000000000..e824ce43b05a
> --- /dev/null
> +++ b/tools/testing/kunit/configs/arch_uml.config
> @@ -0,0 +1,5 @@
> +# Config options which are added to UML builds by default
> +
> +# Enable virtio/pci, as a lot of tests require it.
> +CONFIG_VIRTIO_UML=y
> +CONFIG_UML_PCI_OVER_VIRTIO=y
> diff --git a/tools/testing/kunit/kunit_kernel.py b/tools/testing/kunit/kunit_kernel.py
> index 3539efaf99ba..05e7b1e188d7 100644
> --- a/tools/testing/kunit/kunit_kernel.py
> +++ b/tools/testing/kunit/kunit_kernel.py
> @@ -26,6 +26,7 @@ KUNITCONFIG_PATH = '.kunitconfig'
>  OLD_KUNITCONFIG_PATH = 'last_used_kunitconfig'
>  DEFAULT_KUNITCONFIG_PATH = 'tools/testing/kunit/configs/default.config'
>  BROKEN_ALLCONFIG_PATH = 'tools/testing/kunit/configs/broken_on_uml.config'
> +UML_KCONFIG_PATH = 'tools/testing/kunit/configs/arch_uml.config'
>  OUTFILE_PATH = 'test.log'
>  ABS_TOOL_PATH = os.path.abspath(os.path.dirname(__file__))
>  QEMU_CONFIGS_DIR = os.path.join(ABS_TOOL_PATH, 'qemu_configs')
> @@ -53,7 +54,7 @@ class LinuxSourceTreeOperations:
>                 except subprocess.CalledProcessError as e:
>                         raise ConfigError(e.output.decode())
>
> -       def make_arch_qemuconfig(self, base_kunitconfig: kunit_config.Kconfig) -> None:
> +       def make_arch_config(self, base_kunitconfig: kunit_config.Kconfig) -> None:
>                 pass
>
>         def make_allyesconfig(self, build_dir: str, make_options) -> None:
> @@ -109,7 +110,7 @@ class LinuxSourceTreeOperationsQemu(LinuxSourceTreeOperations):
>                 self._kernel_command_line = qemu_arch_params.kernel_command_line + ' kunit_shutdown=reboot'
>                 self._extra_qemu_params = qemu_arch_params.extra_qemu_params
>
> -       def make_arch_qemuconfig(self, base_kunitconfig: kunit_config.Kconfig) -> None:
> +       def make_arch_config(self, base_kunitconfig: kunit_config.Kconfig) -> None:
>                 kconfig = kunit_config.parse_from_string(self._kconfig)
>                 base_kunitconfig.merge_in_entries(kconfig)
>
> @@ -137,6 +138,10 @@ class LinuxSourceTreeOperationsUml(LinuxSourceTreeOperations):
>         def __init__(self, cross_compile=None):
>                 super().__init__(linux_arch='um', cross_compile=cross_compile)
>
> +       def make_arch_config(self, base_kunitconfig: kunit_config.Kconfig) -> None:
> +               kconfig = kunit_config.parse_file(UML_KCONFIG_PATH)
> +               base_kunitconfig.merge_in_entries(kconfig)
> +
>         def make_allyesconfig(self, build_dir: str, make_options) -> None:
>                 kunit_parser.print_with_timestamp(
>                         'Enabling all CONFIGs for UML...')
> @@ -313,7 +318,7 @@ class LinuxSourceTree:
>                         return self.build_config(build_dir, make_options)
>
>                 existing_kconfig = kunit_config.parse_file(kconfig_path)
> -               self._ops.make_arch_qemuconfig(self._kconfig)
> +               self._ops.make_arch_config(self._kconfig)
>                 if self._kconfig.is_subset_of(existing_kconfig) and not self._kunitconfig_changed(build_dir):
>                         return True
>                 print('Regenerating .config ...')
> --
> 2.37.0.rc0.104.g0611611a94-goog
>