RE: [PATCH v5 09/11] iommu/vt-d: Add iotlb flush for nested domain

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Thursday, September 21, 2023 3:54 PM
> +
> +	/* REVISIT:
> +	 * VT-d has defined ITE, ICE, IQE for invalidation failure per hardware,
> +	 * but no error code yet, so just set the error code to be 0.
> +	 */
> +	*cerror_idx = 0;
> +

Is it "hardware doesn't provide error code now though it's defined in
spec" or "intel-iommu driver doesn't retrieve the error code though
it's provided by the hardware"?

Is there guarantee that '0' isn't used for an existing error code or 
won't be used for any new error code later?