Re: [PATCH v4 5/5] iommu/dma: Force swiotlb_max_mapping_size on an untrusted device

[Christoph Hellwig]

On Wed, Feb 21, 2024 at 11:35:04AM +0000, Will Deacon wrote:
> +static size_t iommu_dma_max_mapping_size(struct device *dev)
> +{
> +	if (is_swiotlb_active(dev) && dev_is_untrusted(dev))
> +		return swiotlb_max_mapping_size(dev);

Curious: do we really need both checks here?  If swiotlb is active
for a device (for whatever reason), aren't we then always bound
by the max size?  If not please add a comment explaining it.