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Date:   Fri, 1 Feb 2019 19:14:33 -0500
From:   Andrea Arcangeli <aarcange@redhat.com>
To:     jglisse@redhat.com
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Peter Xu <peterx@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Michal Hocko <mhocko@kernel.org>, kvm@vger.kernel.org
Subject: Re: [RFC PATCH 0/4] Restore change_pte optimization to its former
 glory
Message-ID: <20190202001433.GB12463@redhat.com>
References: <20190131183706.20980-1-jglisse@redhat.com>
 <20190201235738.GA12463@redhat.com>
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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.