Re: [PATCH] mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages

From: Luck, Tony
Date: Wed Jun 21 2017 - 13:54:14 EST

On Wed, Jun 21, 2017 at 02:12:27AM +0000, Naoya Horiguchi wrote:

> We had better have a reverse operation of this to cancel the unmapping
> when unpoisoning?

When we have unpoisoning, we can add something. We don't seem to have
an inverse function for "set_memory_np" to just flip the _PRESENT bit
back on again. But it would be trivial to write a set_memory_pp().

Since we'd be doing this after the poison has been cleared, we wouldn't
need to play games with the address. We'd just use:

set_memory_pp((unsigned long)pfn_to_kaddr(pfn), 1);