[PATCH] powerpc/powernv: Increase memory block size to 1GB on radix

[Reza Arbab]

On Thu, Sep 07, 2017 at 05:17:41AM +0000, Anton Blanchard wrote:
>But all of memory on PowerNV should be able to be hot unplugged, so
>there are two options as I see it - either increase the memory block
>size, or map everything with 2MB pages.

I may be misunderstanding this, but what if we did something like x86 
does? When trying to unplug a region smaller than the mapping, they fill 
that part of the pagetable with 0xFD instead of freeing the whole thing.  
Once the whole thing is 0xFD, free it.

See arch/x86/mm/init_64.c:remove_{pte,pmd,pud}_table()

---%<---
	memset((void *)addr, PAGE_INUSE, next - addr);

	page_addr = page_address(pte_page(*pte));
	if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
		...
		pte_clear(&init_mm, addr, pte);
		...
	}
---%<---

-- 
Reza Arbab