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Message-ID: <20150527143159.GA1948@gmail.com>
Date: Wed, 27 May 2015 10:32:00 -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 02/36] mmu_notifier: keep track of active invalidation
ranges v3
On Wed, May 27, 2015 at 10:39:23AM +0530, Aneesh Kumar K.V wrote:
> j.glisse@...il.com writes:
>
> > From: Jérôme Glisse <jglisse@...hat.com>
> >
> > The mmu_notifier_invalidate_range_start() and mmu_notifier_invalidate_range_end()
> > can be considered as forming an "atomic" section for the cpu page table update
> > point of view. Between this two function the cpu page table content is unreliable
> > for the address range being invalidated.
> >
> > Current user such as kvm need to know when they can trust the content of the cpu
> > page table. This becomes even more important to new users of the mmu_notifier
> > api (such as HMM or ODP).
>
> I don't see kvm using the new APIs in this patch. Also what is that HMM use this
> for, to protect walking of mirror page table ?. I am sure you are
> covering that in the later patches. May be you may want to mention
> the details here too.
KVM side is not done, i looked at KVM code long time ago and thought oh it
could take advantage of this but now i do not remember exactly. I would need
to check back.
For HMM this is simple, no device fault can populate or walk the mirror page
table on a range that is being invalidated. But concurrent fault/walk can
happen outside the invalidated range. All handled in hmm_device_fault_start().
Cheers,
Jérôme
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