linux-kernel - Re: [PATCH v8 5/8] mm: Device exclusive memory access

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Message-ID: <5737557.YXifvZZQQ8@nvdebian>
Date:   Wed, 19 May 2021 22:46:43 +1000
From:   Alistair Popple <apopple@...dia.com>
To:     Peter Xu <peterx@...hat.com>
CC:     <linux-mm@...ck.org>, <nouveau@...ts.freedesktop.org>,
        <bskeggs@...hat.com>, <akpm@...ux-foundation.org>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <jhubbard@...dia.com>,
        <rcampbell@...dia.com>, <jglisse@...hat.com>, <jgg@...dia.com>,
        <hch@...radead.org>, <daniel@...ll.ch>, <willy@...radead.org>,
        <bsingharora@...il.com>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v8 5/8] mm: Device exclusive memory access

On Wednesday, 19 May 2021 10:21:08 PM AEST Peter Xu wrote:
> External email: Use caution opening links or attachments
> 
> On Wed, May 19, 2021 at 09:35:10PM +1000, Alistair Popple wrote:
> > I think the approach you are describing is similar to what
> > migrate_vma_collect()/migrate_vma_unamp() does now and I think it could be
> > made to work. I ended up going with the GUP+unmap approach in part because
> > Christoph suggested it but primarily because it required less code
> > especially given we needed to call something to fault the page in/break
> > COW anyway (or extend what was there to call handle_mm_fault(), etc.).
> 
> I see, thank. Would you mind add a short paragraph in the commit message
> talking about these two solutions and why we choose the GUP way?

Sure.

 - Alistair

> --
> Peter Xu