diff options
| author | Petr Tesarik <ptesarik@suse.com> | 2026-04-10 13:35:06 +0200 |
|---|---|---|
| committer | Marek Szyprowski <m.szyprowski@samsung.com> | 2026-04-30 08:21:34 +0200 |
| commit | 22d0213e55fbb723c2c00dd5aa855a6eaad95b23 (patch) | |
| tree | e6a1d1cf3c5488b926addeb7f9c8c4f1fca2e799 | |
| parent | 254f49634ee16a731174d2ae34bc50bd5f45e731 (diff) | |
dma-direct: fix use of max_pfn
Calculate the correct physical address of the last byte of memory. Since
max_pfn is in fact "the PFN of the first page after the highest system RAM
in physical address space", the highest address that might be used for a
DMA buffer is one byte below max_pfn << PAGE_SHIFT.
This fix is unlikely to make any difference in practice. It's just that the
current formula is slightly confusing.
Signed-off-by: Petr Tesarik <ptesarik@suse.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20260410113506.262579-1-ptesarik@suse.com
| -rw-r--r-- | kernel/dma/direct.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index ec887f443741..583c5922bca2 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -39,7 +39,7 @@ static inline struct page *dma_direct_to_page(struct device *dev, u64 dma_direct_get_required_mask(struct device *dev) { - phys_addr_t phys = (phys_addr_t)(max_pfn - 1) << PAGE_SHIFT; + phys_addr_t phys = ((phys_addr_t)max_pfn << PAGE_SHIFT) - 1; u64 max_dma = phys_to_dma_direct(dev, phys); return (1ULL << (fls64(max_dma) - 1)) * 2 - 1; @@ -553,7 +553,7 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma, int dma_direct_supported(struct device *dev, u64 mask) { - u64 min_mask = (max_pfn - 1) << PAGE_SHIFT; + u64 min_mask = ((u64)max_pfn << PAGE_SHIFT) - 1; /* * Because 32-bit DMA masks are so common we expect every architecture |