machine_os: Preemptively load vfio kernel module.

[mkalcok]

VFIO kernel module is not always loaded, which causes tests to fail when they try to set No-IOMMU mode. This change calls modprobe to ensure that VFIO is loaded before we try to use it.

[fnordahl]

Would an alternative be to use the already existing load_kernel_module() function for this?:

zaza/zaza/utilities/machine_os.py

Lines 38 to 54 in 51c90db

	def load_kernel_module(unit_name, module_name, module_arguments=None,
	model_name=None):
	"""Load kernel module on unit.
	:param unit_name: Name of unit to operate on
	:type unit_name: str
	:param module_name: Name of kernel module to load
	:type module_name: str
	:param module_arguments: Extra arguments to pass to module on load
	:type module_arguments: Optional[str]
	:param model_name: Name of model to query
	:type model_name: Optional[str]
	:returns: The function is called for its side effects and does not return.
	:raises: zaza.model.CommandRunFailed
	"""
	cmd = 'modprobe {} {}'.format(module_name, module_arguments or '')
	zaza.utilities.juju.remote_run(unit_name, cmd, model_name=model_name)

And does the call belong here or on the test code (have no strong opinions on this one, just raising the question).

[mkalcok]

Oh, good point about the load_kernel_module, I missed that.
Regarding the placement, I think that this is the right place. Up until now the tests called enable_vfio_unsafe_noiommu_mode with the assumption that the VFIO module is loaded. Loading the kernel here ensures that the assumption is correct (+ there are no side effects to trying to load already loaded module).

[mkalcok]

I wonder what changed since the last time the CI passed. I don't see any changes, yet linting fails on parts of the code that wasn't changed in this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.50%. Comparing base (4f05c70) to head (b20ec47).
Report is 9 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #678   +/-   ##
=======================================
  Coverage   89.50%   89.50%           
=======================================
  Files          42       42           
  Lines        4717     4718    +1     
=======================================
+ Hits         4222     4223    +1     
  Misses        495      495           

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[fnordahl]

LGTM, and thank you for the code gardening required by new flake8 unblocking the zaza gate!