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Message-ID: <20151022141111.GA2914@redhat.com> Date: Thu, 22 Oct 2015 10:11:11 -0400 From: Jerome Glisse <jglisse@...hat.com> To: Randy Dunlap <rdunlap@...radead.org> 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>, 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>, Leonid Shamis <Leonid.Shamis@....com>, Laurent Morichetti <Laurent.Morichetti@....com>, Alexander Deucher <Alexander.Deucher@....com> Subject: Re: [PATCH v11 15/15] HMM: add documentation explaining HMM internals and how to use it. On Wed, Oct 21, 2015 at 08:23:41PM -0700, Randy Dunlap wrote: > Hi, > > Some corrections and a few questions... Thanks for the corrections. Answer below. > On 10/21/15 14:00, Jérôme Glisse wrote: > > This add documentation on how HMM works and a more in depth view of how it > > should be use by device driver writers. > > > > Signed-off-by: Jérôme Glisse <jglisse@...hat.com> [...] > > +synchronizing device page table for range that the device driver explicitly ask > > ranges asks > > or is only one range supported? Several ranges are supported. [...] > > + /* Mirror memory (in read mode) between addressA and addressB */ > > + your_hmm_event->hmm_event.start = addressA; > > + your_hmm_event->hmm_event.end = addressB; > > Multiple events (ranges) can be specified? Device driver have to make one call per range but multiple threads can make concurrent call for different ranges. > Is hmm_event.end (addressB) included or excluded from the range? Forgot to copy comment from header file, start is inclusive, end is exclusive. [...] > > + struct hmm_pt_iter iter; > > + hmm_pt_iter_init(&iter, &mirror->pt) > > + > > + /* Get pointer to HMM page table entry for a given address. */ > > + dma_addr_t *hmm_pte; > > + hmm_pte = hmm_pt_iter_walk(&iter, &addr, &next); > > what are 'addr' and 'next'? (types) unsigned long will add then to the doc, good point. [...] > > + /* Migrate system memory between addressA and addressB to device memory. */ > > + your_hmm_event->hmm_event.start = addressA; > > + your_hmm_event->hmm_event.end = addressB; > > is hmm_event.end (addressB) inclusive and exclusive? > i.e., is it end_of_copy + 1? > i.e., is the size of the copy addressB - addressA or > addressB - addressA + 1? > i.e., is addressB = addressA + size > or is addressB = addressA + size - 1 Exclusive last one. > In my experience it is usually better to have a start_address and size > instead of start_address and end_address. I switched several time btw the 2 offer differents version of the patchset, it is something that can be change down the road unless you have strong feeling about it. Cheers, Jérôme -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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