On second thought, this code does have problems with highmem. The page in
question was never kmapped, so no kernel address was assigned if the page
was a high memory page. Besides that, there are other other changes to
page address that imply it can't be used with a high memory page. So the
above code isn't generic.
> I
> belive that it should not be problem because I am mmap'ing kmalloc'ed memory
> which always returns mapped memory. But whats happeing in my lab is
> different. If I define HIGHMEM in kernel configuration and install 2GB of
> memory in my server then I see a crash in the kernel where I try to access
> kaddr calculated bu above code. Any idea?
Because of what I just said.
> The problem with your suggestion is that at the point where user gives me an
> address for DMA, I do not know what kmalloc_buffer and vma->vm_start values
> are. Also, if there are more than one processes accessing the driver, then
> how am I going to keep track of all mmap'ed memory.
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