Re: [PATCH v6 07/17] iommu/arm-smmu-v3: Track ATC invalidation timeouts in a bitmap

[sashiko-bot@kernel.org]

> An ATC invalidation timeout is a fatal error. While the SMMUv3 hardware is
> aware of the timeout via a GERROR interrupt, the driver thread issuing the
> commands lacks a direct mechanism to verify whether its specific batch was
> the cause or not, as polling the CMD_SYNC status doesn't natively return a
> failure code, making it very difficult to coordinate per-device recovery.
> 
> Introduce an atc_sync_timeouts bitmap in the cmdq structure to bridge this
> gap. When the ISR detects an ATC timeout, set the bit corresponding to the
> physical CMDQ index of the faulting CMD_SYNC command.
> 
> On the issuer side, test the bit after the poll completes or times out, and
> return -EIO when it is set, so the caller can quarantine the device. Order
> the test after the poll with an smp_rmb(), since the poll may use a relaxed
> load. Test before clearing, to spare the shared cache line an atomic RMW in
> the common no-timeout case.
> 
> Clear any stale bit before publishing a new CMD_SYNC in a reused slot, so
> the GERROR handler can only mark the new command.
> 
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

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

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