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Date:   Fri, 1 Feb 2019 19:14:33 -0500
From:   Andrea Arcangeli <aarcange@...hat.com>
To:     jglisse@...hat.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Peter Xu <peterx@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Michal Hocko <mhocko@...nel.org>, kvm@...r.kernel.org
Subject: Re: [RFC PATCH 0/4] Restore change_pte optimization to its former
 glory

On Fri, Feb 01, 2019 at 06:57:38PM -0500, Andrea Arcangeli wrote:
> If it's cleared with ptep_clear_flush_notify, change_pte still won't
> work. The above text needs updating with
> "ptep_clear_flush". set_pte_at_notify is all about having
> ptep_clear_flush only before it or it's the same as having a range
> invalidate preceding it.
> 
> With regard to the code, wp_page_copy() needs
> s/ptep_clear_flush_notify/ptep_clear_flush/ before set_pte_at_notify.

Oops, the above two statements were incorrect because
ptep_clear_flush_notify doesn't interfere with change_pte and will
only invalidate secondary MMU mappings on those secondary MMUs that
shares the same pagetables with the primary MMU and that in turn won't
ever implement a change_pte method.

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