linux-kernel - Re: [PATCH v3 3/3] mm/mmu_notifier: contextual information for event triggering invalidation v2

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Date:   Thu, 13 Dec 2018 09:21:12 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Jérôme Glisse <jglisse@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>, zwisler@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>, rkrcmar@...hat.com,
        Michal Hocko <mhocko@...nel.org>,
        "Koenig, Christian" <christian.koenig@....com>,
        rcampbell@...dia.com, John Hubbard <jhubbard@...dia.com>,
        KVM list <kvm@...r.kernel.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v3 3/3] mm/mmu_notifier: contextual information for event
 triggering invalidation v2

On Thu, Dec 13, 2018 at 9:14 AM <jglisse@...hat.com> wrote:
>
> From: Jérôme Glisse <jglisse@...hat.com>
>
> CPU page table update can happens for many reasons, not only as a result
> of a syscall (munmap(), mprotect(), mremap(), madvise(), ...) but also
> as a result of kernel activities (memory compression, reclaim, migration,
> ...).
>
> Users of mmu notifier API track changes to the CPU page table and take
> specific action for them. While current API only provide range of virtual
> address affected by the change, not why the changes is happening.
>
> This patchset adds event information so that users of mmu notifier can
> differentiate among broad category:
>     - UNMAP: munmap() or mremap()
>     - CLEAR: page table is cleared (migration, compaction, reclaim, ...)
>     - PROTECTION_VMA: change in access protections for the range
>     - PROTECTION_PAGE: change in access protections for page in the range
>     - SOFT_DIRTY: soft dirtyness tracking
>
> Being able to identify munmap() and mremap() from other reasons why the
> page table is cleared is important to allow user of mmu notifier to
> update their own internal tracking structure accordingly (on munmap or
> mremap it is not longer needed to track range of virtual address as it
> becomes invalid).

Who consumes these new enum values? The consumer of the new
infrastructure should be included in the patchset that adds the new
functionality. So a NAK from me until the consumer is clarified /
included.