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author committer Nicolin Chen 2020-09-01 15:16:45 -0700 Christoph Hellwig 2020-09-03 18:12:15 +0200 1e9d90dbed120ec98517428ffff4dacd9797e39d (patch) d743be6b54427bb62e36e6d1ae2f6fc243cd70b7 /arch/alpha/kernel 2281f797f5524abb8fff66bf8540b4f4687332a2 (diff) linux-stericsson-1e9d90dbed120ec98517428ffff4dacd9797e39d.tar.gz
dma-mapping: introduce dma_get_seg_boundary_nr_pages()
We found that callers of dma_get_seg_boundary mostly do an ALIGN with page mask and then do a page shift to get number of pages: ALIGN(boundary + 1, 1 << shift) >> shift However, the boundary might be as large as ULONG_MAX, which means that a device has no specific boundary limit. So either "+ 1" or passing it to ALIGN() would potentially overflow. According to kernel defines: #define ALIGN_MASK(x, mask) (((x) + (mask)) & ~(mask)) #define ALIGN(x, a) ALIGN_MASK(x, (typeof(x))(a) - 1) We can simplify the logic here into a helper function doing: ALIGN(boundary + 1, 1 << shift) >> shift = ALIGN_MASK(b + 1, (1 << s) - 1) >> s = {[b + 1 + (1 << s) - 1] & ~[(1 << s) - 1]} >> s = [b + 1 + (1 << s) - 1] >> s = [b + (1 << s)] >> s = (b >> s) + 1 This patch introduces and applies dma_get_seg_boundary_nr_pages() as an overflow-free helper for the dma_get_seg_boundary() callers to get numbers of pages. It also takes care of the NULL dev case for non-DMA API callers. Suggested-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com> Acked-by: Niklas Schnelle <schnelle@linux.ibm.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'arch/alpha/kernel')
-rw-r--r--arch/alpha/kernel/pci_iommu.c7
1 files changed, 1 insertions, 6 deletions
 diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.cindex 81037907268d..6f7de4f4e191 100644--- a/arch/alpha/kernel/pci_iommu.c+++ b/arch/alpha/kernel/pci_iommu.c@@ -141,12 +141,7 @@ iommu_arena_find_pages(struct device *dev, struct pci_iommu_arena *arena, unsigned long boundary_size; base = arena->dma_base >> PAGE_SHIFT;- if (dev) {- boundary_size = dma_get_seg_boundary(dev) + 1;- boundary_size >>= PAGE_SHIFT;- } else {- boundary_size = 1UL << (32 - PAGE_SHIFT);- }+ boundary_size = dma_get_seg_boundary_nr_pages(dev, PAGE_SHIFT); /* Search forward for the first mask-aligned sequence of N free ptes */ ptes = arena->ptes;