On 08/11/2022 02.06, David Matlack wrote:
On Fri, Oct 14, 2022 at 09:03:59PM +0000, Sean Christopherson wrote:
On Tue, Oct 04, 2022, Thomas Huth wrote:
Many KVM selftests are completely silent. This has the disadvantage
for the users that they do not know what's going on here. For example,
some time ago, a tester asked me how to know whether a certain new
sub-test has been added to one of the s390x test binaries or not (which
he didn't compile on his own), which is hard to judge when there is no
output. So I finally went ahead and implemented TAP output in the
s390x-specific tests some months ago.
Now I wonder whether that could be a good strategy for the x86 and
generic tests, too?
Taking Andrew's thoughts a step further, I'm in favor of adding TAP output, but
only if we implement it in such a way that it reduces the burden on writing new
tests. I _really_ like that sync_regs_test's subtests are split into consumable
chunks, but I worry that the amount of boilerplate needed will deter test writes
and increase the maintenance cost.
And my experience with KVM-unit-tests is that letting test writers specify strings
for test names is a bad idea, e.g. using an arbitrary string creates a disconnect
between what the user sees and what code is running, and makes it unnecessarily
difficult to connect a failure back to code. And if we ever support running
specific testcases by name (I'm still not sure this is a net positive), arbitrary
strings get really annoying because inevitably an arbitrary string will contain
characters that need to be escaped in the shell.
Adding a macro or three to let tests define and run testscases with minimal effort
would more or less eliminate the boilerplate. And in theory providing semi-rigid
macros would help force simple tests to conform to standard patterns, which should
reduce the cost of someone new understanding the test, and would likely let us do
more automagic things in the future.
E.g. something like this in the test:
KVM_RUN_TESTCASES(vcpu,
test_clear_kvm_dirty_regs_bits,
test_set_invalid,
test_req_and_verify_all_valid_regs,
test_set_and_verify_various_reg_values,
test_clear_kvm_dirty_regs_bits,
);
There is an existing framework in
tools/testing/selftests/kselftest_harness.h that provides macros for
setting up and running tests cases. I converted sync_regs_test to use it
below as an example [1].
The harness runs each subtest in a child process, so sharing a VM/VCPU
across test cases is not possible. This means setting up and tearing
down a VM for every test case, but the harness makes this pretty easy
with FIXTURE_{SETUP,TEARDOWN}(). With this harness, we can keep using
TEST_ASSERT() as-is, and still run all test cases even if one fails.
Plus no need for the hard-coded ksft_*() calls in main().
Hi!
Sorry for not getting back to this earlier - I'm pretty much busy with other
stuff right now. But your suggestion looks really cool, I like it - so if
you've got some spare time to work on the conversion, please go ahead (I
won't have much time to work on this in the next weeks, I think)!
Thomas
