On Wed, Aug 12, 2026 at 10:22:03AM +0800, Reinette Chatre wrote: > 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 <[email protected]> > > Reviewed-by: Ilpo Järvinen <[email protected]> > > Signed-off-by: Richard Cheng <[email protected]> > > --- > > This patch is unchanged from v3. My comments against v3 still apply: > https://lore.kernel.org/lkml/[email protected]/ > > 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
Hi Reinette, Thanks for your patient and review. Just to confirm that I understand correctly before I send v5. I plan to 1. Split this patch out of the arm64 series and send it as a standalone v5 patch 2. Keep the code change the same, and udpate the commit message to make it clear that having no exclusive cache portion causes L3_CAT to fail, and simplify the desciprtion as you suggested 3. Change the in-code comment to platform-neutral wording About the editted commit message, I plan to write it like the following """ selftests/resctrl: Skip L3_CAT when no exclusive cache portion exists 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. Some platforms legitimately report every cache bit as shareable, leaving no exclusive cache portion and causing L3_CAT to fail. Skip, rather than fail, the L3_CAT test when the platform has no exclusive cache portion that the test can use. """ Does this match what you imagined ? Best regards, Richard Cheng.
