Re: [PATCH v5 15/18] iommu/arm-smmu-v3: Add INV_TYPE_ATS_BROKEN to skip quarantined ATS masters

[sashiko-bot@kernel.org]

> A subsequent change quarantines a master whose ATC invalidation timed out,
> marking its INV_TYPE_ATS / INV_TYPE_ATS_FULL entries in that domain's invs
> as broken. Clearing STE.EATS makes the SMMU reject the device's ATS but
> does not stop the driver from issuing ATC_INV, so without a marker those
> commands would keep timing out on that master.
> 
> Add the INV_TYPE_ATS_BROKEN type. __arm_smmu_domain_inv_range() skips it in
> its switch without issuing commands. arm_smmu_inv_is_ats() recognizes it so
> the iter's batch-boundary logic places it next to other ATS group entries.
> 
> The setter writes cur->type via WRITE_ONCE while the inv_range iter holds
> read_lock on invs->rwlock, so its loads of cur->type and next->type race
> with it. A new arm_smmu_inv_type() helper wraps the load in READ_ONCE, and
> the iter and arm_smmu_inv_cmp() read through it. cur->type is u8 so the
> access is already atomic; READ_ONCE annotates it for KCSAN and matches the
> [ ... ]
> anywhere.
> 
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Assisted-by: Claude:claude-opus-4-7
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

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

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