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Date:   Tue, 14 Jul 2020 21:29:30 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Ira Weiny <ira.weiny@intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
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Subject: Re: [RFC PATCH 12/15] kmap: Add stray write protection for device
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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 ...