hmm_test issues with latest mainline

[Vlastimil Babka <vbabka@suse.cz>]

Hi,

I've been trying the hmm_tests as of today's commit:

a185a0995518 ("Merge tag 'linux-kselftest-kunit-6.1-rc1-2' ...)

and run into several issues that seemed worth reporting.

First, it seems the FIXTURE_TEARDOWN(hmm) in
tools/testing/selftests/vm/hmm-tests.c
using ASSERT_EQ(ret, 0); can run into an infinite loop of reporting the
assertion failure. Dunno if it's a kselftests issue or it's a bug to
use asserts in teardown. I hacked it up like this locally to proceed:

--- a/tools/testing/selftests/vm/hmm-tests.c
+++ b/tools/testing/selftests/vm/hmm-tests.c
@@ -154,6 +154,11 @@ FIXTURE_TEARDOWN(hmm)
 {
 	int ret = close(self->fd);
 
+	if (ret != 0) {
+		fprintf(stderr, "close returned (%d) fd is (%d)\n", ret,self->fd);
+		exit(1);
+	}
+
 	ASSERT_EQ(ret, 0);
 	self->fd = -1;
 }

Next, there are some tests that fail (and thus also trigger the issue above)

#  RUN           hmm.hmm_device_private.exclusive ...
# hmm-tests.c:1702:exclusive:Expected ret (-16) == 0 (0)
close returned (-1) fd is (3)
# exclusive: Test failed at step #1
#          FAIL  hmm.hmm_device_private.exclusive
not ok 20 hmm.hmm_device_private.exclusive
#  RUN           hmm.hmm_device_private.exclusive_mprotect ...
# hmm-tests.c:1756:exclusive_mprotect:Expected ret (-16) == 0 (0)
close returned (-1) fd is (3)
# exclusive_mprotect: Test failed at step #1
#          FAIL  hmm.hmm_device_private.exclusive_mprotect
not ok 21 hmm.hmm_device_private.exclusive_mprotect
#  RUN           hmm.hmm_device_private.exclusive_cow ...
# hmm-tests.c:1809:exclusive_cow:Expected ret (-16) == 0 (0)
close returned (-1) fd is (3)
# exclusive_cow: Test failed at step #1
#          FAIL  hmm.hmm_device_private.exclusive_cow
not ok 22 hmm.hmm_device_private.exclusive_cow

I'll try to check more closely but maybe if you can reproduce it too, you'll
have more idea what's going on.

The next thing is more of a question/documentation suggestion. Tons of tests
fail like this:

ok 24 hmm.hmm_device_private.hmm_cow_in_device
#  RUN           hmm.hmm_device_coherent.open_close ...
could not open hmm dmirror driver (/dev/hmm_dmirror2)
#      SKIP      DEVICE_COHERENT not available
#            OK  hmm.hmm_device_coherent.open_close

I assume this is because I run "test_hmm.sh smoke" without the SPM parameters.
The help message doesn't say much about what to specify there for
<spm_addr_dev0> <spm_addr_dev1>. Do these tests need a particular hardware?
(unlike the rest?) Maybe it could be clarified.

Last thing, I noticed all these DEVICE_COHERENT tests ultimately count as OK,
not SKIPPED, which would probably be more appropriate?

# FAILED: 51 / 54 tests passed.
# Totals: pass:50 fail:3 xfail:0 xpass:0 skip:1 error:0

(the skip:1 is due to test 9 "#      SKIP      Huge page could not be allocated"
which is probably a misconfiguration on my part so I don't report that as an issue)

Thanks,
Vlastimil