linux-kernel - Re: [PATCH 03/36] mmu_notifier: pass page pointer to mmu_notifier_invalidate

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Date:	Wed, 27 May 2015 10:33:43 -0400
From:	Jerome Glisse <j.glisse@...il.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Linus Torvalds <torvalds@...ux-foundation.org>,
	joro@...tes.org, Mel Gorman <mgorman@...e.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <jweiner@...hat.com>,
	Larry Woodman <lwoodman@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Dave Airlie <airlied@...hat.com>,
	Brendan Conoboy <blc@...hat.com>,
	Joe Donohue <jdonohue@...hat.com>,
	Duncan Poole <dpoole@...dia.com>,
	Sherry Cheung <SCheung@...dia.com>,
	Subhash Gutti <sgutti@...dia.com>,
	John Hubbard <jhubbard@...dia.com>,
	Mark Hairgrove <mhairgrove@...dia.com>,
	Lucien Dunning <ldunning@...dia.com>,
	Cameron Buschardt <cabuschardt@...dia.com>,
	Arvind Gopalakrishnan <arvindg@...dia.com>,
	Haggai Eran <haggaie@...lanox.com>,
	Shachar Raindel <raindel@...lanox.com>,
	Liran Liss <liranl@...lanox.com>,
	Roland Dreier <roland@...estorage.com>,
	Ben Sander <ben.sander@....com>,
	Greg Stoner <Greg.Stoner@....com>,
	John Bridgman <John.Bridgman@....com>,
	Michael Mantor <Michael.Mantor@....com>,
	Paul Blinzer <Paul.Blinzer@....com>,
	Laurent Morichetti <Laurent.Morichetti@....com>,
	Alexander Deucher <Alexander.Deucher@....com>,
	Oded Gabbay <Oded.Gabbay@....com>,
	Jérôme Glisse <jglisse@...hat.com>
Subject: Re: [PATCH 03/36] mmu_notifier: pass page pointer to
 mmu_notifier_invalidate_page()

On Wed, May 27, 2015 at 10:47:44AM +0530, Aneesh Kumar K.V wrote:
> j.glisse@...il.com writes:
> 
> > From: Jérôme Glisse <jglisse@...hat.com>
> >
> > Listener of mm event might not have easy way to get the struct page
> > behind and address invalidated with mmu_notifier_invalidate_page()
> > function as this happens after the cpu page table have been clear/
> > updated. This happens for instance if the listener is storing a dma
> > mapping inside its secondary page table. To avoid complex reverse
> > dma mapping lookup just pass along a pointer to the page being
> > invalidated.
> 
> .....
> 
> > diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> > index ada3ed1..283ad26 100644
> > --- a/include/linux/mmu_notifier.h
> > +++ b/include/linux/mmu_notifier.h
> > @@ -172,6 +172,7 @@ struct mmu_notifier_ops {
> >  	void (*invalidate_page)(struct mmu_notifier *mn,
> >  				struct mm_struct *mm,
> >  				unsigned long address,
> > +				struct page *page,
> >  				enum mmu_event event);
> >  
> 
> How do we handle this w.r.t invalidate_range ? 

With range invalidation the CPU page table is still reliable when
invalidate_range_start() callback happen. So we can lookup the CPU
page table to get the page backing the address.

Cheers,
Jérôme
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