Re: [PATCH v4 1/3] selftests/resctrl: Skip L3_CAT when no exclusive cache portion exists

[Reinette Chatre]

Hi Richard,

On 7/21/26 8:59 PM, Richard Cheng wrote:
> L3_CAT measures cache isolation, which requires at least one cache bit
> that is not shared with non-CPU agents, i.e. cbm_mask & ~shareable_bits
> must be non-zero. On MPAM, shareable_bits == cbm_mask is a legitimate
> state, so there are situations in which no bit can be reported as
> exclusive.
> 
> Previously get_mask_no_shareable() was invoked inside cat_run_test()
> and silently returned -1, which surfaced as a test failure on arm64
> MPAM systems.
> 
> Implement cat_feature_check() to perform the same check at feature-check
> time. It prints a diagnostic and returns false so the test case is
> skipped instead of failing.
> 
> Tested-by: Chen Yu <yu.c.chen@xxxxxxxxx>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> Signed-off-by: Richard Cheng <icheng@xxxxxxxxxx>
> ---

This patch is unchanged from v3. My comments against v3 still apply:
https://lore.kernel.org/lkml/5d76e776-82d3-4f02-8384-a890349ae96c@xxxxxxxxx/

As noted there, this issue does not just impact aarch64. Could you please
split this patch from this series? When it is ready I would like to make a
request for its inclusion in the next cycle.

Thank you.

Reinette