Re: [PATCH v5 04/15] iommu/arm-smmu-v3: Drain in-flight fault events on domain detach

[sashiko-bot@kernel.org]

> When a device leaves a domain, fault events for the old domain may remain
> in the SMMU event queue or the IOPF workqueue. If the IOMMU core frees that
> domain before those events are handled, the work may use freed memory.
> 
> Start with the hardware queue by using arm_smmu_wait_for_queue_drained() to
> count entries consumed by the threaded IRQ handler, and poll the EVTQ when
> an IOPF-enabled attachment ends. This prevents a pending IRQ from queuing
> old-domain work after the drain. Its until_empty mode can drain the CMDQ as
> well during suspend and runtime PM.
> 
> queue_poll() cannot be used because it is an atomic busy-wait that expects
> hardware to consume entries. The EVTQ and PRIQ are drained by threaded IRQ
> handlers, so a busy-wait could starve a handler sharing the same CPU on a
> non-preemptible kernel. The new helper sleeps, and might_sleep() catches an
> atomic-context caller even when the queue is already empty.
> [ ... ]
> Fixes: cfea71aea921 ("iommu/arm-smmu-v3: Put iopf enablement in the domain attach path")
> Cc: stable@vger.kernel.org # v6.16
> Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
> Assisted-by: LLM
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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