linux-kernel - Re: [PATCH v4 05/16] iommu/dma: rename iommu_dma_*map_page to iommu_dma_*map

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250828133857.GD9469@nvidia.com>
Date: Thu, 28 Aug 2025 10:38:57 -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 v4 05/16] iommu/dma: rename iommu_dma_*map_page to
 iommu_dma_*map_phys

On Tue, Aug 19, 2025 at 08:36:49PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
> 
> Rename the IOMMU DMA mapping functions to better reflect their actual
> calling convention. The functions iommu_dma_map_page() and
> iommu_dma_unmap_page() are renamed to iommu_dma_map_phys() and
> iommu_dma_unmap_phys() respectively, as they already operate on physical
> addresses rather than page structures.
> 
> The calling convention changes from accepting (struct page *page,
> unsigned long offset) to (phys_addr_t phys), which eliminates the need
> for page-to-physical address conversion within the functions. This
> renaming prepares for the broader DMA API conversion from page-based
> to physical address-based mapping throughout the kernel.
> 
> All callers are updated to pass physical addresses directly, including
> dma_map_page_attrs(), scatterlist mapping functions, and DMA page
> allocation helpers. The change simplifies the code by removing the
> page_to_phys() + offset calculation that was previously done inside
> the IOMMU functions.
> 
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>  drivers/iommu/dma-iommu.c | 14 ++++++--------
>  include/linux/iommu-dma.h |  7 +++----
>  kernel/dma/mapping.c      |  4 ++--
>  kernel/dma/ops_helpers.c  |  6 +++---
>  4 files changed, 14 insertions(+), 17 deletions(-)

This looks fine

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

But related to other patches..

iommu_dma_map_phys() ends up like this:

	if (dev_use_swiotlb(dev, size, dir) &&
	    iova_unaligned(iovad, phys, size)) {
		if (attrs & DMA_ATTR_MMIO)
			return DMA_MAPPING_ERROR;

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

But attrs is passed all the way down to swiotlb_tbl_map_single(),
maybe the DMA_ATTR_MMIO check should be moved there?

There are a few call chains with this redundancy:

dma_iova_link()
 -> iommu_dma_iova_link_swiotlb
  -> iommu_dma_iova_bounce_and_link
   -> iommu_dma_map_swiotlb
    -> swiotlb_tbl_map_single()

iommu_dma_map_phys() 
   -> iommu_dma_map_swiotlb
    -> swiotlb_tbl_map_single()

dma_direct_map_phys()
 -> swiotlb_map()
  -> swiotlb_tbl_map_single()

It makes alot of sense to put the check for MMIO when
slots[].orig_addr is stored because that is the point where we start
to require a pfn_to_page().

Jason