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

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Date:   Tue, 4 Dec 2018 09:48:55 -0500
From:   Jerome Glisse <jglisse@...hat.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Ross Zwisler <zwisler@...nel.org>, Jan Kara <jack@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Christian Koenig <christian.koenig@....com>,
        Felix Kuehling <felix.kuehling@....com>,
        Ralph Campbell <rcampbell@...dia.com>,
        John Hubbard <jhubbard@...dia.com>, kvm@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 3/3] mm/mmu_notifier: contextual information for event
 triggering invalidation

On Tue, Dec 04, 2018 at 10:17:48AM +0200, Mike Rapoport wrote:
> On Mon, Dec 03, 2018 at 03:18:17PM -0500, jglisse@...hat.com wrote:
> > From: Jérôme Glisse <jglisse@...hat.com>

[...]

> > diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> > index cbeece8e47d4..3077d487be8b 100644
> > --- a/include/linux/mmu_notifier.h
> > +++ b/include/linux/mmu_notifier.h
> > @@ -25,10 +25,43 @@ struct mmu_notifier_mm {
> >  	spinlock_t lock;
> >  };
> > 
> > +/*
> > + * What event is triggering the invalidation:
> 
> Can you please make it kernel-doc comment?

Sorry should have done that in the first place, Andrew i will post a v2
with that and fixing my one stupid bug.



> > + *
> > + * MMU_NOTIFY_UNMAP
> > + *    either munmap() that unmap the range or a mremap() that move the range
> > + *
> > + * MMU_NOTIFY_CLEAR
> > + *    clear page table entry (many reasons for this like madvise() or replacing
> > + *    a page by another one, ...).
> > + *
> > + * MMU_NOTIFY_PROTECTION_VMA
> > + *    update is due to protection change for the range ie using the vma access
> > + *    permission (vm_page_prot) to update the whole range is enough no need to
> > + *    inspect changes to the CPU page table (mprotect() syscall)
> > + *
> > + * MMU_NOTIFY_PROTECTION_PAGE
> > + *    update is due to change in read/write flag for pages in the range so to
> > + *    mirror those changes the user must inspect the CPU page table (from the
> > + *    end callback).
> > + *
> > + *
> > + * MMU_NOTIFY_SOFT_DIRTY
> > + *    soft dirty accounting (still same page and same access flags)
> > + */
> > +enum mmu_notifier_event {
> > +	MMU_NOTIFY_UNMAP = 0,
> > +	MMU_NOTIFY_CLEAR,
> > +	MMU_NOTIFY_PROTECTION_VMA,
> > +	MMU_NOTIFY_PROTECTION_PAGE,
> > +	MMU_NOTIFY_SOFT_DIRTY,
> > +};