[PATCH v9 03/24] iommu: generalize the batched sync after map interface

[Jason Gunthorpe]

On Wed, Apr 23, 2025 at 11:12:54AM +0300, Leon Romanovsky wrote:
> From: Christoph Hellwig <hch at lst.de>
> 
> For the upcoming IOVA-based DMA API we want to use the interface batch the
> sync after mapping multiple entries from dma-iommu without having a
> scatterlist.

Grammer:

 For the upcoming IOVA-based DMA API we want to batch the
 ops->iotlb_sync_map() call after mapping multiple IOVAs from
 dma-iommu without having a scatterlist. Improve the API.

 Add a wrapper for the map_sync as iommu_sync_map() so that callers don't
 need to poke into the methods directly.

 Formalize __iommu_map() into iommu_map_nosync() which requires the
 caller to call iommu_sync_map() after all maps are completed.

 Refactor the existing sanity checks from all the different layers
 into iommu_map_nosync().

>  drivers/iommu/iommu.c | 65 +++++++++++++++++++------------------------
>  include/linux/iommu.h |  4 +++
>  2 files changed, 33 insertions(+), 36 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg at nvidia.com>

> +	/* Discourage passing strange GFP flags */
> +	if (WARN_ON_ONCE(gfp & (__GFP_COMP | __GFP_DMA | __GFP_DMA32 |
> +				__GFP_HIGHMEM)))
> +		return -EINVAL;

There is some kind of overlap with the new iommu_alloc_pages_node()
here that does a similar check, nothing that can be addressed in this
series but maybe a TBD for later..

Jason