kselftest: add capability to skip chosen TARGETS

Let the user specify an optional TARGETS skiplist through the new optional
SKIP_TARGETS Makefile variable.

It is easier to skip at will using a reduced and well defined list of
possibly problematic targets with SKIP_TARGETS than to provide a partially
stripped down list of good targets using the usual TARGETS variable.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Documentation/dev-tools/kselftest.rst

@@ -89,6 +89,22 @@ To build, save output files in a separate directory with KBUILD_OUTPUT ::
 
   $ export KBUILD_OUTPUT=/tmp/kselftest; make TARGETS="size timers" kselftest
 
+Additionally you can use the "SKIP_TARGETS" variable on the make command
+line to specify one or more targets to exclude from the TARGETS list.
+
+To run all tests but a single subsystem::
+
+  $ make -C tools/testing/selftests SKIP_TARGETS=ptrace run_tests
+
+You can specify multiple tests to skip::
+
+  $  make SKIP_TARGETS="size timers" kselftest
+
+You can also specify a restricted list of tests to run together with a
+dedicated skiplist::
+
+  $  make TARGETS="bpf breakpoints size timers" SKIP_TARGETS=bpf kselftest
+
 See the top-level tools/testing/selftests/Makefile for the list of all
 possible targets.
 

tools/testing/selftests/Makefile

@@ -63,6 +63,13 @@ TARGETS += zram
 TARGETS_HOTPLUG = cpu-hotplug
 TARGETS_HOTPLUG += memory-hotplug
 
+# User can optionally provide a TARGETS skiplist.
+SKIP_TARGETS ?=
+ifneq ($(SKIP_TARGETS),)
+	TMP := $(filter-out $(SKIP_TARGETS), $(TARGETS))
+	override TARGETS := $(TMP)
+endif
+
 # Clear LDFLAGS and MAKEFLAGS if called from main
 # Makefile to avoid test build failures when test
 # Makefile doesn't have explicit build rules.