Re: [PATCH v2 04/10] iommupt: Flush the CPU cache after any writes to the page table

[Baolu Lu <baolu.lu@linux.intel.com>]

On 8/27/25 01:26, Jason Gunthorpe wrote:
> @@ -585,6 +635,7 @@ static __always_inline int __do_map_single_page(struct pt_range *range,
>   			return -EADDRINUSE;
>   		pt_install_leaf_entry(&pts, map->oa, PAGE_SHIFT,
>   				      &map->attrs);
> +		/* No flush, not used when incoherent */
>   		map->oa += PAGE_SIZE;
>   		return 0;
>   	}
> @@ -811,7 +862,8 @@ int DOMAIN_NS(map_pages)(struct iommu_domain *domain, unsigned long iova,
>   	PT_WARN_ON(map.leaf_level > range.top_level);
>   
>   	do {
> -		if (single_page) {
> +		if (single_page &&
> +		    !pt_feature(common, PT_FEAT_DMA_INCOHERENT)) {
>   			ret = pt_walk_range(&range, __map_single_page, &map);
>   			if (ret != -EAGAIN)
>   				break;

I don't follow the single_page logic here. Why is single_page exclusive
with PT_FEAT_DMA_INCOHERENT? To my understanding, PT_FEAT_DMA_INCOHERENT
has no relationship with how the page table is organized. Could you
elaborate a bit?

Thanks,
baolu