Re: [PATCH] mm: Add new vma flag VM_LOCAL_CPU

[Peter Zijlstra]

On Tue, May 15, 2018 at 01:43:23PM +0300, Boaz Harrosh wrote:
> Yes I know, but that is exactly the point of this flag. I know that this
> address is only ever accessed from a single core. Because it is an mmap (vma)
> of an O_TMPFILE-exclusive file created in a core-pinned thread and I allow
> only that thread any kind of access to this vma. Both the filehandle and the
> mmaped pointer are kept on the thread stack and have no access from outside.
> 
> So the all point of this flag is the kernel driver telling mm that this
> address is enforced to only be accessed from one core-pinned thread.

What happens when the userspace part -- there is one, right, how else do
you get an mm to stick a vma in -- simply does a full address range
probe scan?

Something like this really needs a far more detailed Changelog that
explains how its to be used and how it is impossible to abuse. Esp. that
latter is _very_ important.