[PATCH v2 2/2] selftests/powerpc: Add test to verify rfi flush across a system call

[Michael Ellerman]

"Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> writes:
> Michael Ellerman wrote:
>> "Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> writes:
>>> diff --git a/tools/testing/selftests/powerpc/security/rfi_flush.c b/tools/testing/selftests/powerpc/security/rfi_flush.c
>>> new file mode 100644
>>> index 000000000000..a20fe8eca161
>>> --- /dev/null
>>> +++ b/tools/testing/selftests/powerpc/security/rfi_flush.c
>>> @@ -0,0 +1,132 @@
>> ...
>>> +
>>> +int rfi_flush_test(void)
>>> +{
>>> +	char *p;
>>> +	int repetitions = 10;
>>> +	int fd, passes = 0, iter, rc = 0;
>>> +	struct perf_event_read v;
>>> +	uint64_t l1d_misses_total = 0;
>>> +	unsigned long iterations = 100000, zero_size = 24*1024;
>>> +	int rfi_flush_org, rfi_flush;
>>> +
>>> +	SKIP_IF(geteuid() != 0);
>>> +
>>> +	if (read_debugfs_file("powerpc/rfi_flush", &rfi_flush_org)) {
>>> +		perror("error reading powerpc/rfi_flush debugfs file");
>>> +	        printf("unable to determine current rfi_flush setting");
>>> +		return 1;
>>> +	}
>> 
>> This leads to a hard error on old kernels, which I don't want (breaks my CI).
>
> Hmm... didn't realize new tests would be run on older kernels. Are those 
> older stable/distro releases, or actually just earlier kernel versions?

All of the above :)

Obviously keeping all the tests working across all kernel versions ever
is impossible, but when it's relatively easy like in this case, it's
nice to do.

So that was mostly just an FYI, I don't expect test writers to get their
tests running across all kernel versions.

cheers