Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function

From: Dave Hansen
Date: Mon Jun 10 2019 - 18:07:15 EST

On 6/10/19 1:58 PM, Yu-cheng Yu wrote:
>>> On each memory request, the kernel then must consider a percentage of
>>> allocated space in its calculation, and on systems with less memory
>>> this quickly becomes a problem.
>> I'm not sure what you're referring to here? Are you referring to our
>> overcommit limits?
> Yes.

My assumption has always been that these large, potentially sparse
hardware tables *must* be mmap()'d with MAP_NORESERVE specified. That
should keep them from being problematic with respect to overcommit.