How can I tell kmalloc to use big (>2M) pages?
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I am writing a device driver to allocate a large buffer for DMA.  My system is using (or so I believe) 4k pages, and I want it to use larger pages, i.e. at least 2M pages.

How can I:

* enable large pages in the system (or check if they're enabled)?
* specify that the current `kmalloc` should use large pages?

