On Tue, Aug 19, 2025 at 08:36:44PM +0300, Leon Romanovsky wrote:
> This series does the core code and modern flows. A followup series
> will give the same treatment to the legacy dma_ops implementation.
I took a quick check over this to see that it is sane. I think using
phys is an improvement for most of the dma_ops implemenations.
arch/sparc/kernel/pci_sun4v.c
arch/sparc/kernel/iommu.c
Uses __pa to get phys from the page, never touches page
arch/alpha/kernel/pci_iommu.c
arch/sparc/mm/io-unit.c
drivers/parisc/ccio-dma.c
drivers/parisc/sba_iommu.c
Does page_addres() and later does __pa on it. Doesn't touch struct page
arch/x86/kernel/amd_gart_64.c
drivers/xen/swiotlb-xen.c
arch/mips/jazz/jazzdma.c
Immediately does page_to_phys(), never touches struct page
drivers/vdpa/vdpa_user/vduse_dev.c
Does page_to_phys() to call iommu_map()
drivers/xen/grant-dma-ops.c
Does page_to_pfn() and nothing else
arch/powerpc/platforms/ps3/system-bus.c
This is a maze but I think it wants only phys and the virt is only
used for debug prints.
The above all never touch a KVA and just want a phys_addr_t.
The below are touching the KVA somehow:
arch/sparc/mm/iommu.c
arch/arm/mm/dma-mapping.c
Uses page_address to cache flush, would be happy with phys_to_virt()
and a PhysHighMem()
arch/powerpc/kernel/dma-iommu.c
arch/powerpc/platforms/pseries/vio.c
Uses iommu_map_page() which wants phys_to_virt(), doesn't touch
struct page
arch/powerpc/platforms/pseries/ibmebus.c
Returns phys_to_virt() as dma_addr_t.
The two PPC ones are weird, I didn't figure out how that was working..
It would be easy to make map_phys patches for about half of these, in
the first grouping. Doing so would also grant those arches
map_resource capability.
Overall I didn't think there was any reduction in maintainability in
these places. Most are improvements eliminating code, and some are
just switching to phys_to_virt() from page_address(), which we could
further guard with DMA_ATTR_MMIO and a check for highmem.
Jason
