selftests/resctrl: Make benchmark parameter passing robust

The benchmark used during the CMT, MBM, and MBA tests can be provided by
the user via (-b) parameter, if not provided the default "fill_buf"
benchmark is used. The user is additionally able to override
any of the "fill_buf" default parameters when running the tests with
"-b fill_buf <fill_buf parameters>".

The "fill_buf" parameters are managed as an array of strings. Using an
array of strings is complex because it requires transformations to/from
strings at every producer and consumer. This is made worse for the
individual tests where the default benchmark parameters values may not
be appropriate and additional data wrangling is required. For example,
the CMT test duplicates the entire array of strings in order to replace
one of the parameters.

More issues appear when combining the usage of an array of strings with
the use case of user overriding default parameters by specifying
"-b fill_buf <parameters>". This use case is fragile with opportunities
to trigger a SIGSEGV because of opportunities for NULL pointers to exist
in the array of strings. For example, by running below (thus by specifying
"fill_buf" should be used but all parameters are NULL):
	$ sudo resctrl_tests -t mbm -b fill_buf

Replace the "array of strings" parameters used for "fill_buf" with
new struct fill_buf_param that contains the "fill_buf" parameters that
can be used directly without transformations to/from strings. Two
instances of struct fill_buf_param may exist at any point in time:
	* If the user provides new parameters to "fill_buf", the
	  user parameter structure (struct user_params) will point to a
	  fully initialized and immutable struct fill_buf_param
	  containing the user provided parameters.
	* If "fill_buf" is the benchmark that should be used by a test,
	  then the test parameter structure (struct resctrl_val_param)
	  will point to a fully initialized struct fill_buf_param. The
	  latter may contain (a) the user provided parameters verbatim,
	  (b) user provided parameters adjusted to be appropriate for
	  the test, or (c) the default parameters for "fill_buf" that
	  is appropriate for the test if the user did not provide
	  "fill_buf" parameters nor an alternate benchmark.

The existing behavior of CMT test is to use test defined value for the
buffer size even if the user provides another value via command line.
This behavior is maintained since the test requires that the buffer size
matches the size of the cache allocated, and the amount of cache
allocated can instead be changed by the user with the "-n" command line
parameter.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions