Hi Peter,
On 04/25/2013 06:51 AM, H. Peter Anvin wrote:

On 04/10/2013 01:02 AM, Minchan Kim wrote:

When I am looking at the code, I was wonder about the logic of GHZP(aka,
get_huge_zero_page) reference handling. The logic depends on that page
allocator never alocate PFN 0.

Who makes sure it? What happens if allocator allocates PFN 0?
I don't know all of architecture makes sure it.
You investigated it for all arches?

This isn't manifest, right?  At least on x86 we should never, ever
allocate PFN 0.

I see in memblock_trim_memory(): start = round_up(orig_start, align); here align is PAGE_SIZE, so the dump of zone ranges in my machine is [ 0.000000] DMA [mem 0x00001000-0x00ffffff]. Why PFN 0 is not used? just for align?


	-hpa


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