Re: [PATCH v3] sparc: Fix page alignment in dma mapping

[Han Gao]

> On Feb 18, 2026, at 20:00, stian@xxxxxx wrote:
> 
> From: Stian Halseth <stian@xxxxxx>
> 
> 'phys' may include an offset within the page, while 'base_paddr' is already
> page-aligned. This caused incorrect DMA mapping in dma_4u_map_phys and
> dma_4v_map_phys.
> 
> Fix both functions by masking phys with IO_PAGE_MASK or subtracting the
> page offset, covering both generic SPARC code and sun4v.
> 
> Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
> Reported-by: Stian Halseth <stian@xxxxxx>
> Closes: https://github.com/sparclinux/issues/issues/75
> Suggested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Signed-off-by: Stian Halseth <stian@xxxxxx>
> ---
> Changelog:
> v3:
> - Use IO_PAGE_MASK for alignment in both dma_4u_map_phys and dma_4v_map_phys
> - Align phys before the loop in pci_sun4v.c
> - Drop masking inside iommu_batch_add()
> 
> v2: https://lore.kernel.org/all/20260217171104.5643-3-stian@xxxxxx/
> - Add Fixes tag
> - Add Closes tag
> - Trim commit message to 80-column lines
> - Remove newlines
> - Subject: Remove the "iommu/pci_sun4v:" (generic sparc patch, not specific to sun4v)
> 
> v1: https://lore.kernel.org/all/20260217150350.3541-2-stian@xxxxxx/ 
> ---
> arch/sparc/kernel/iommu.c     | 2 ++
> arch/sparc/kernel/pci_sun4v.c | 2 ++
> 2 files changed, 4 insertions(+)
> 
> diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
> index 46ef88bc9c26..7613ab0ffb89 100644
> --- a/arch/sparc/kernel/iommu.c
> +++ b/arch/sparc/kernel/iommu.c
> @@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device *dev, phys_addr_t phys,
> if (direction != DMA_TO_DEVICE)
> iopte_protection |= IOPTE_WRITE;
> 
> + phys &= IO_PAGE_MASK;
> +
> for (i = 0; i < npages; i++, base++, phys += IO_PAGE_SIZE)
> iopte_val(*base) = iopte_protection | phys;
> 
> diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
> index 791f0a76665f..58ca4148f86b 100644
> --- a/arch/sparc/kernel/pci_sun4v.c
> +++ b/arch/sparc/kernel/pci_sun4v.c
> @@ -410,6 +410,8 @@ static dma_addr_t dma_4v_map_phys(struct device *dev, phys_addr_t phys,
> 
> iommu_batch_start(dev, prot, entry);
> 
> + phys &= IO_PAGE_MASK;
> +
> for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
> long err = iommu_batch_add(phys, mask);
> if (unlikely(err < 0L))
> -- 
> 2.53.0
> 
> 

Tested-by: Han Gao <gaohan@xxxxxxxxxxx> # on SPARC Enterprise T5220