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

["Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>]

Michael Ellerman wrote:
> "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> writes:
>> Michael Ellerman wrote:
>>> "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> writes:
>>>> diff --git a/tools/testing/selftests/powerpc/security/rfi_flush.c b/to=
ols/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 =3D 10;
>>>> +	int fd, passes =3D 0, iter, rc =3D 0;
>>>> +	struct perf_event_read v;
>>>> +	uint64_t l1d_misses_total =3D 0;
>>>> +	unsigned long iterations =3D 100000, zero_size =3D 24*1024;
>>>> +	int rfi_flush_org, rfi_flush;
>>>> +
>>>> +	SKIP_IF(geteuid() !=3D 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;
>>>> +	}
>>>=20
>>> This leads to a hard error on old kernels, which I don't want (breaks m=
y CI).
>>
>> Hmm... didn't realize new tests would be run on older kernels. Are those=
=20
>> older stable/distro releases, or actually just earlier kernel versions?
>=20
> All of the above :)
>=20
> 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.
>=20
> So that was mostly just an FYI, I don't expect test writers to get their
> tests running across all kernel versions.

Good to know, thanks!
- Naveen

=