benh at kernel
Aug 4, 2012, 5:16 PM
Post #1 of 3
(65 views)
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Is iommu_num_pages() broken ?
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Hi folks !
I stumbled upon this today:
static inline unsigned long iommu_num_pages(unsigned long addr,
unsigned long len,
unsigned long io_page_size)
{
unsigned long size = (addr & (io_page_size - 1)) + len;
return DIV_ROUND_UP(size, io_page_size);
}
That doesn't look right to me...
The powerpc iommu code at least uses that with an addr which may not be
page aligned (ie, result of sg_virt() which include the offset).
The above code will align the start before adding the len which is wrong
and will result in potentially missing a page or am I missing
something ?
Shouldn't it be something like
static inline unsigned long iommu_num_pages(unsigned long addr,
unsigned long len,
unsigned long io_page_size)
{
unsigned long start = addr & (io_page_size - 1);
unsigned long end = addr + len;
return DIV_ROUND_UP(end - start, io_page_size);
}
?
Cheers,
Ben.
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