linux-kernel - Re: [PATCH v12 07/29] HMM: add per mirror page table v4.

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Date:	Tue, 29 Mar 2016 15:58:30 -0700
From:	John Hubbard <jhubbard@...dia.com>
To:	Jérôme Glisse <jglisse@...hat.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>,
	Christophe Harle <charle@...dia.com>,
	Duncan Poole <dpoole@...dia.com>,
	Sherry Cheung <SCheung@...dia.com>,
	Subhash Gutti <sgutti@...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>,
	Leonid Shamis <Leonid.Shamis@....com>,
	Laurent Morichetti <Laurent.Morichetti@....com>,
	Alexander Deucher <Alexander.Deucher@....com>,
	Jatin Kumar <jakumar@...dia.com>
Subject: Re: [PATCH v12 07/29] HMM: add per mirror page table v4.

On Tue, 8 Mar 2016, Jérôme Glisse wrote:

> This patch add the per mirror page table. It also propagate CPU page
> table update to this per mirror page table using mmu_notifier callback.
> All update are contextualized with an HMM event structure that convey
> all information needed by device driver to take proper actions (update
> its own mmu to reflect changes and schedule proper flushing).
> 
> Core HMM is responsible for updating the per mirror page table once
> the device driver is done with its update. Most importantly HMM will
> properly propagate HMM page table dirty bit to underlying page.
> 
> Changed since v1:
>   - Removed unused fence code to defer it to latter patches.
> 
> Changed since v2:
>   - Use new bit flag helper for mirror page table manipulation.
>   - Differentiate fork event with HMM_FORK from other events.
> 
> Changed since v3:
>   - Get rid of HMM_ISDIRTY and rely on write protect instead.
>   - Adapt to HMM page table changes
> 
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Signed-off-by: Sherry Cheung <SCheung@...dia.com>
> Signed-off-by: Subhash Gutti <sgutti@...dia.com>
> Signed-off-by: Mark Hairgrove <mhairgrove@...dia.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> Signed-off-by: Jatin Kumar <jakumar@...dia.com>
> ---
>  include/linux/hmm.h |  83 ++++++++++++++++++++
>  mm/hmm.c            | 221 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 304 insertions(+)
> 
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index b559c0b..5488fa9 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -46,6 +46,7 @@
>  #include <linux/mmu_notifier.h>
>  #include <linux/workqueue.h>
>  #include <linux/mman.h>
> +#include <linux/hmm_pt.h>
>  
>  
>  struct hmm_device;
> @@ -53,6 +54,38 @@ struct hmm_mirror;
>  struct hmm;
>  
>  
> +/*
> + * hmm_event - each event is described by a type associated with a struct.
> + */
> +enum hmm_etype {
> +	HMM_NONE = 0,
> +	HMM_FORK,
> +	HMM_MIGRATE,
> +	HMM_MUNMAP,
> +	HMM_DEVICE_RFAULT,
> +	HMM_DEVICE_WFAULT,

Hi Jerome,

Just a tiny thing I noticed, while connecting HMM to NVIDIA's upcoming 
device driver: the last two enum items above should probably be named 
like this:

	HMM_DEVICE_READ_FAULT,
	HMM_DEVICE_WRITE_FAULT,

instead of _WFAULT / _RFAULT. (Earlier code reviewers asked for more 
clarity on these types of names.)

thanks,
John Hubbard

> +	HMM_WRITE_PROTECT,
> +};
> +