Re: [RFC PATCH 12/15] kmap: Add stray write protection for device pages

Peter Zijlstra
2020-07-14T19:29:44Z

On Tue, Jul 14, 2020 at 12:06:16PM -0700, Ira Weiny wrote:
> On Tue, Jul 14, 2020 at 10:44:51AM +0200, Peter Zijlstra wrote:

> > So, if I followed along correctly, you're proposing to do a WRMSR per
> > k{,un}map{_atomic}(), sounds like excellent performance all-round :-(
>
> Only to pages which have this additional protection, ie not DRAM.
>
> User mappings of this memory is not affected (would be covered by User PKeys if
> desired). User mappings to persistent memory are the primary use case and the
> performant path.

Because performance to non-volatile memory doesn't matter? I think Dave
has a better answer here ...