linux-kernel - Re: [PATCH v6 7/8] mm/mmu_notifier: pass down vma and reasons why mmu notifier is happening v2

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Message-ID: <20190411054130.GY3201@mtr-leonro.mtl.com>
Date:   Thu, 11 Apr 2019 08:41:30 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     jglisse@...hat.com, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Christian König <christian.koenig@....com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>, Jan Kara <jack@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Ross Zwisler <zwisler@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Ralph Campbell <rcampbell@...dia.com>,
        John Hubbard <jhubbard@...dia.com>, kvm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v6 7/8] mm/mmu_notifier: pass down vma and reasons why
 mmu notifier is happening v2

On Wed, Apr 10, 2019 at 04:41:57PM -0700, Ira Weiny wrote:
> On Tue, Mar 26, 2019 at 12:47:46PM -0400, Jerome Glisse 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 patch is just passing down the new informations by adding it to the
> > mmu_notifier_range structure.
> >
> > Changes since v1:
> >     - Initialize flags field from mmu_notifier_range_init() arguments
> >
> > Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: linux-mm@...ck.org
> > Cc: Christian König <christian.koenig@....com>
> > Cc: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
> > Cc: Jani Nikula <jani.nikula@...ux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@...el.com>
> > Cc: Jan Kara <jack@...e.cz>
> > Cc: Andrea Arcangeli <aarcange@...hat.com>
> > Cc: Peter Xu <peterx@...hat.com>
> > Cc: Felix Kuehling <Felix.Kuehling@....com>
> > Cc: Jason Gunthorpe <jgg@...lanox.com>
> > Cc: Ross Zwisler <zwisler@...nel.org>
> > Cc: Dan Williams <dan.j.williams@...el.com>
> > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: Radim Krčmář <rkrcmar@...hat.com>
> > Cc: Michal Hocko <mhocko@...nel.org>
> > Cc: Christian Koenig <christian.koenig@....com>
> > Cc: Ralph Campbell <rcampbell@...dia.com>
> > Cc: John Hubbard <jhubbard@...dia.com>
> > Cc: kvm@...r.kernel.org
> > Cc: dri-devel@...ts.freedesktop.org
> > Cc: linux-rdma@...r.kernel.org
> > Cc: Arnd Bergmann <arnd@...db.de>
> > ---
> >  include/linux/mmu_notifier.h | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> > index 62f94cd85455..0379956fff23 100644
> > --- a/include/linux/mmu_notifier.h
> > +++ b/include/linux/mmu_notifier.h
> > @@ -58,10 +58,12 @@ struct mmu_notifier_mm {
> >  #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
> >
> >  struct mmu_notifier_range {
> > +	struct vm_area_struct *vma;
> >  	struct mm_struct *mm;
> >  	unsigned long start;
> >  	unsigned long end;
> >  	unsigned flags;
> > +	enum mmu_notifier_event event;
> >  };
> >
> >  struct mmu_notifier_ops {
> > @@ -363,10 +365,12 @@ static inline void mmu_notifier_range_init(struct mmu_notifier_range *range,
> >  					   unsigned long start,
> >  					   unsigned long end)
> >  {
> > +	range->vma = vma;
> > +	range->event = event;
> >  	range->mm = mm;
> >  	range->start = start;
> >  	range->end = end;
> > -	range->flags = 0;
> > +	range->flags = flags;
>
> Which of the "user patch sets" uses the new flags?
>
> I'm not seeing that user yet.  In general I don't see anything wrong with the
> series and I like the idea of telling drivers why the invalidate has fired.
>
> But is the flags a future feature?

It seems that it is used in HMM ODP patch.
https://patchwork.kernel.org/patch/10894281/

Thanks

>
> For the series:
>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
>
> Ira
>
> >  }
> >
> >  #define ptep_clear_flush_young_notify(__vma, __address, __ptep)		\
> > --
> > 2.20.1
> >

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