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Date: Thu, 30 Jul 2026 18:10:30 +0100
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Subject: Re: [PATCH v6 00/10] arm_mpam: Add MPAM-Fb firmware support
To: Andre Przywara <andre.przywara@arm.com>,
 Lorenzo Pieralisi <lpieralisi@kernel.org>, Hanjun Guo
 <guohanjun@huawei.com>, Sudeep Holla <sudeep.holla@kernel.org>,
 Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>,
 "Rafael J . Wysocki" <rafael@kernel.org>, Len Brown <lenb@kernel.org>,
 James Morse <james.morse@arm.com>,
 Reinette Chatre <reinette.chatre@intel.com>, Fenghua Yu <fenghuay@nvidia.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
 Srivathsa L Rao <srivathsa.rao@oss.qualcomm.com>,
 Ganapatrao Kulkarni <ganapatrao.kulkarni@oss.qualcomm.com>,
 Trilok Soni <tsoni@quicinc.com>, Srinivas Ramana <sramana@qti.qualcomm.com>,
 Niyas Sait <niyas.sait@arm.com>, Lee Trager <lee@trager.us>,
 Ritwick Sharma <ritwick.sharma@arm.com>, linux-acpi@vger.kernel.org,
 linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20260730152539.2712312-1-andre.przywara@arm.com>
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From: Ben Horgan <ben.horgan@arm.com>
In-Reply-To: <20260730152539.2712312-1-andre.przywara@arm.com>
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Hi Andre,

On 7/30/26 16:25, Andre Przywara wrote:
[...]
> The first six patches rework all MSC access wrappers to propagate error
> information. Pure MMIO based MSC accesses would never fail, but the
> MPAM-Fb access can go wrong in multiple ways. The patches have been split
> up purely for reviewing reasons, if the number is a problem, we could as
> well squash them. Please note that until the very last patch of this series
> any MSC accesses would always only return 0, it's only the final enablement
> of MPAM-Fb that could possibly introduce errors. Hence all former patches
> can add error handling gradually, those code paths wouldn't be triggered
> before patch 10/10.

I had a go at injecting some errors and noticed that at least some aren't getting to user space.
When writing the schemata file any MPAM-Fb error is not propagated to the user. The
resctrl_arch_update_domains() continues to return 0 as there are some missing links in the chain
down to the writes, e.g. __write_config() always returns 0.

Thanks,

Ben