From: Reinette Chatre <reinette.chatre@intel.com>
To: Richard Cheng <icheng@nvidia.com>, <tony.luck@intel.com>,
<x86@kernel.org>
Cc: Dave.Martin@arm.com, james.morse@arm.com, babu.moger@amd.com,
shuah@kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, newtonl@nvidia.com,
kristinc@nvidia.com, kobak@nvidia.com, kaihengf@nvidia.com,
fenghuay@nvidia.com, ltrager@nvidia.com,
"Chen Yu" <yu.c.chen@intel.com>,
"Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Subject: Re: [PATCH v4 1/3] selftests/resctrl: Skip L3_CAT when no exclusive cache portion exists
Date: Wed, 12 Aug 2026 10:22:03 -0700 [thread overview]
Message-ID: <1eb20140-66e6-4e2e-b6e9-5172cfa29bbc@intel.com> (raw)
In-Reply-To: <20260722035943.32337-2-icheng@nvidia.com>
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@intel.com>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Signed-off-by: Richard Cheng <icheng@nvidia.com>
> ---
This patch is unchanged from v3. My comments against v3 still apply:
https://lore.kernel.org/lkml/5d76e776-82d3-4f02-8384-a890349ae96c@intel.com/
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
next prev parent reply other threads:[~2026-08-12 17:22 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-22 3:59 [PATCH v4 0/3] selftests/resctrl: Fix resctrl selftests issues on aarch64 Richard Cheng
2026-07-22 3:59 ` [PATCH v4 1/3] selftests/resctrl: Skip L3_CAT when no exclusive cache portion exists Richard Cheng
2026-08-12 17:22 ` Reinette Chatre [this message]
2026-07-22 3:59 ` [PATCH v4 2/3] selftests/resctrl: Implement cl_flush() and sb() for aarch64 Richard Cheng
2026-08-12 17:25 ` Reinette Chatre
2026-07-22 3:59 ` [PATCH v4 3/3] selftests/resctrl: Recognise aarch64 as a vendor for L3_NONCONT_CAT Richard Cheng
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