linux-kernel - Re: [PATCH v1 05/16] iommu/dma: rename iommu_dma_*map_page to iommu_dma_*map

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Message-ID: <20250806184443.GD184255@nvidia.com>
Date: Wed, 6 Aug 2025 15:44:43 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
	Leon Romanovsky <leonro@...dia.com>,
	Abdiel Janulgue <abdiel.janulgue@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>, Danilo Krummrich <dakr@...nel.org>,
	iommu@...ts.linux.dev, Jason Wang <jasowang@...hat.com>,
	Jens Axboe <axboe@...nel.dk>, Joerg Roedel <joro@...tes.org>,
	Jonathan Corbet <corbet@....net>, Juergen Gross <jgross@...e.com>,
	kasan-dev@...glegroups.com, Keith Busch <kbusch@...nel.org>,
	linux-block@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-nvme@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
	linux-trace-kernel@...r.kernel.org,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Robin Murphy <robin.murphy@....com>, rust-for-linux@...r.kernel.org,
	Sagi Grimberg <sagi@...mberg.me>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	virtualization@...ts.linux.dev, Will Deacon <will@...nel.org>,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v1 05/16] iommu/dma: rename iommu_dma_*map_page to
 iommu_dma_*map_phys

On Mon, Aug 04, 2025 at 03:42:39PM +0300, Leon Romanovsky wrote:
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 399838c17b705..11c5d5f8c0981 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1190,11 +1190,9 @@ static inline size_t iova_unaligned(struct iova_domain *iovad, phys_addr_t phys,
>  	return iova_offset(iovad, phys | size);
>  }
>  
> -dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> -	      unsigned long offset, size_t size, enum dma_data_direction dir,
> -	      unsigned long attrs)
> +dma_addr_t iommu_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
> +		enum dma_data_direction dir, unsigned long attrs)
>  {
> -	phys_addr_t phys = page_to_phys(page) + offset;
>  	bool coherent = dev_is_dma_coherent(dev);
>  	int prot = dma_info_to_prot(dir, coherent, attrs);
>  	struct iommu_domain *domain = iommu_get_dma_domain(dev);

No issue with pushing the page_to_phys to the looks like two callers..

It is worth pointing though that today if the page * was a
MEMORY_DEVICE_PCI_P2PDMA page then it is illegal to call the swiotlb
functions a few lines below this:

                phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);

ie struct page alone as a type is not sufficient to make this function
safe for a long time now.

So I would add some explanation in the commit message how this will be
situated in the final call chains, and maybe leave behind a comment
that attrs may not have ATTR_MMIO in this function.

I think the answer is iommu_dma_map_phys() is only called for
!ATTR_MMIO addresses, and that iommu_dma_map_resource() will be called
for ATTR_MMIO?

Jason