Re: [RFC/PATCH 2/7] iommu-api: Add map_range/unmap_range functions

[Hiroshi Doyu <hdoyu@nvidia.com>]

Hi Olav,

Olav Haugan <ohaugan@codeaurora.org> writes:

> Mapping and unmapping are more often than not in the critical path.
> map_range and unmap_range allows SMMU driver implementations to optimize
> the process of mapping and unmapping buffers into the SMMU page tables.
> Instead of mapping one physical address, do TLB operation (expensive),
> mapping, do TLB operation, mapping, do TLB operation the driver can map
> a scatter-gatherlist of physically contiguous pages into one virtual
> address space and then at the end do one TLB operation.
>
> Additionally, the mapping operation would be faster in general since
> clients does not have to keep calling map API over and over again for
> each physically contiguous chunk of memory that needs to be mapped to a
> virtually contiguous region.
>
> Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
> ---
>  drivers/iommu/iommu.c | 24 ++++++++++++++++++++++++
>  include/linux/iommu.h | 24 ++++++++++++++++++++++++
>  2 files changed, 48 insertions(+)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index e5555fc..f2a6b80 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -898,6 +898,30 @@ size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova, size_t size)
>  EXPORT_SYMBOL_GPL(iommu_unmap);
>  
>  
> +int iommu_map_range(struct iommu_domain *domain, unsigned int iova,
> +		    struct scatterlist *sg, unsigned int len, int prot)
> +{
> +	if (unlikely(domain->ops->map_range == NULL))
> +		return -ENODEV;
> +
> +	BUG_ON(iova & (~PAGE_MASK));
> +
> +	return domain->ops->map_range(domain, iova, sg, len, prot);
> +}
> +EXPORT_SYMBOL_GPL(iommu_map_range);

We have the similar one internally, which is named, "iommu_map_sg()",
called from DMA API.

> +int iommu_unmap_range(struct iommu_domain *domain, unsigned int iova,
> +		      unsigned int len)
> +{
> +	if (unlikely(domain->ops->unmap_range == NULL))
> +		return -ENODEV;
> +
> +	BUG_ON(iova & (~PAGE_MASK));
> +
> +	return domain->ops->unmap_range(domain, iova, len);
> +}
> +EXPORT_SYMBOL_GPL(iommu_unmap_range);

Can the existing iommu_unmap() do the same?