On 9/5/24 14:43, Reinette Chatre wrote:
Hi Shuah,
On 9/5/24 11:06 AM, Shuah Khan wrote:
On 9/4/24 06:54, Ilpo Järvinen wrote:
On Wed, 4 Sep 2024, Shuah Khan wrote:
On 9/4/24 06:18, Ilpo Järvinen wrote:
On Tue, 3 Sep 2024, Shuah Khan wrote:
On 9/3/24 08:45, Ilpo Järvinen wrote:
This series first generalizes resctrl selftest non-contiguous CAT check
to not assume non-AMD vendor implies Intel. Second, it improves
selftests such that the use of __cpuid_count() does not lead into a
build failure (happens at least on ARM).
While ARM does not currently support resctrl features, there's an
ongoing work to enable resctrl support also for it on the kernel side.
In any case, a common header such as kselftest.h should have a proper
fallback in place for what it provides, thus it seems justified to fix
this common level problem on the common level rather than e.g.
disabling build for resctrl selftest for archs lacking resctrl support.
I've dropped reviewed and tested by tags from the last patch in v3 due
to major changes into the makefile logic. So it would be helpful if
Muhammad could retest with this version.
Acquiring ARCH in lib.mk will likely allow some cleanup into some
subdirectory makefiles but that is left as future work because this
series focuses in fixing cpuid/build.
v4:
- New patch to reorder x86 selftest makefile to avoid clobbering CFLAGS
(would cause __cpuid_count() related build fail otherwise)
I don't like the way this patch series is mushrooming. I am not
convinced that changes to lib.mk and x86 Makefile are necessary.
I didn't like it either what I found from the various makefiles. I think
there are many things done which conflict with what lib.mk seems to try to
do.
Some of it by desig. lib.mk offers framework for common things. There
are provisions to override like in the case of x86, powerpc. lib.mk
tries to be flexible as well.
I tried to ask in the first submission what test I should use in the
header file as I'm not very familiar with how arch specific is done in
userspace in the first place nor how it should be done within kselftest
framework.
Thoughts on cpuid:
- It is x86 specific. Moving this to kselftest.h was done to avoid
duplicate. However now we are running into arm64/arm compile
errors due to this which need addressing one way or the other.
I have some ideas on how to solve this - but I need answers to
the following questions.
This is a question for you and Usama.
- Does resctrl run on arm64/arm and what's the output?
- Can all other tests in resctrl other tests except
noncont_cat_run_test?
- If so send me the output.
Hi Shuah,
As mentioned in my coverletter above, resctrl does not currently support
arm but there's an ongoing work to add arm support. On kernel side it
requires major refactoring to move non-arch specific stuff out from
arch/x86 so has (predictably) taken long time.
The resctrl selftests are mostly written in arch independent way (*) but
there's also a way to limit a test only to CPUs from a particular vendor.
And now this noncont_cat_run_test needs to use cpuid only on Intel CPUs
(to read the supported flag), it's not needed even on AMD CPUs as they
always support non-contiguous CAT bitmask.
So to summarize, it would be possible to disable resctrl test for non-x86
but it does not address the underlying problem with cpuid which will just
come back later I think.
Alternatively, if there's some a good way in C code to do ifdeffery around
that cpuid call, I could make that too, but I need to know which symbol to
use for that ifdef.
(*) The cache topology may make some selftest unusable on new archs but
not the selftest code itself.
I agree that suppressing resctrl build is not a solution. The real problem
is is in defining __cpuid_count() in common code path.
I fixed it and send patch in. As I was testing I noticed the following on
AMD platform:
- it ran the L3_NONCONT_CAT test which is expected.
# # Starting L3_NONCONT_CAT test ...
# # Mounting resctrl to "/sys/fs/resctrl"
# ARCH_AMD - supports non-contiguous CBM
# # Write schema "L3:0=ff" to resctrl FS
# # Write schema "L3:0=fc3f" to resctrl FS
# ok 5 L3_NONCONT_CAT: test
- It went on to run L2_NONCONT_CAT - failed
It is not intended to appear as a failure but instead just skipping of
a test since the platform does not support the feature being tested.
# ok 6 # SKIP Hardware does not support L2_NONCONT_CAT or L2_NONCONT_CAT is disabled
The output looks as intended. When I run the test on an Intel system without
L2 CAT the output looks the same.
Does it make sense to run both L3_NONCONT_CAT and L2_NONCONT_CAT
on AMD? Maybe it is? resctrl checks L3 or L2 support on Intel.
The selftests test the features as exposed by the generic resctrl kernel
subsystem instead of relying on its own inventory of what features
need to be checked for which vendor. selftests will thus only
test L3 or L2 if resctrl kernel subsystem indicates it is supported on
underlying platform. Only afterwards may it use platform specific
knowledge to help validate the feature.
In this scenario resctrl indicated that L2 CAT is not supported
by underlying platform and the test was skipped. It looks good
to me.
Thanks for the detailed explanation. Sounds good to me.
thanks,
-- Shuah
