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

On 18.02.2026 13:00, [email protected] wrote:
> From: Stian Halseth <[email protected]>
>
> '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 <[email protected]>
> Closes: https://protect2.fireeye.com/v1/url?k=7ae4b721-1b6fa20e-7ae53c6e-74fe485cbfe7-9b567c88f1f84114&q=1&e=1e25ada4-9521-4797-a8c9-57719379250d&u=https%3A%2F%2Fgithub.com%2Fsparclinux%2Fissues%2Fissues%2F75
> Suggested-by: Marek Szyprowski <[email protected]>
> Signed-off-by: Stian Halseth <[email protected]>

Applied to dma-mapping-fixes branch with slightly adjusted commit 
description (to match v3 changes). Thanks!

> ---
> 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/[email protected]/
> - 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/[email protected]/
> ---
>   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))

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland