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

[Boaz Harrosh <boazh@netapp.com>]

On 15/05/18 14:47, Peter Zijlstra wrote:
> 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.
> 

Thank you yes. I will try and capture all this thread in the commit message
and as Christoph demanded supply a user code to demonstrate usage.

Thank you for looking
Boaz