diff options
| author | Nicolin Chen <nicoleotsuka@gmail.com> | 2020-09-01 15:16:45 -0700 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2020-09-03 18:12:15 +0200 |
| commit | 1e9d90dbed120ec98517428ffff4dacd9797e39d (patch) | |
| tree | d743be6b54427bb62e36e6d1ae2f6fc243cd70b7 /arch/alpha | |
| parent | 2281f797f5524abb8fff66bf8540b4f4687332a2 (diff) | |
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')
| -rw-r--r-- | arch/alpha/kernel/pci_iommu.c | 7 |
1 files changed, 1 insertions, 6 deletions
diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.c index 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; |