linux-kernel - Re: [PULL] topic/iomem-mmap-vs-gup

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Message-ID: <CAKMK7uFsRPod-tAJ8ZrzXM6B_+5VgvRs-U0_TiG75da62cnVnw@mail.gmail.com>
Date:   Mon, 17 May 2021 17:29:35 +0200
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     Christoph Hellwig <hch@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PULL] topic/iomem-mmap-vs-gup

On Mon, May 10, 2021 at 9:30 AM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Mon, May 10, 2021 at 09:16:58AM +0200, Daniel Vetter wrote:
> > > End result: not pulling it, unless somebody can explain to me in small
> > > words why I'm wrong and have the mental capacity of a damaged rodent.
> >
> > No rodents I think, just more backstory of how this all fits. tldr;
> > pin_user_pages is the only safe use of this vb2 userptr thing.
>
> Yes, which is why I advocate for just ripping the follow_pfn path
> out entirely.  It could have been used for crazy ad dangerous peer to
> peer transfers outside of any infrastructure making it safe, or for
> pre-CMA kernel memory carveouts for lage contiguous memory allocations
> (which are pretty broken by design as well).  So IMHO the only sensible
> thing is to remove this cruft entirely, and if it breaks a currently
> working setup (which I think is unlikely) we'll have to make sure it
> can work the proper way.

Since I'm not getting any cozy consenus vibes here on any option I
think I'll just drop this.

Stephen, can you pls drop

git://anongit.freedesktop.org/drm/drm topic/iomem-mmap-vs-gup

from linux-next? It's not going anywhere. I'll also go ahead and
delete the branch, to make sure you catch this update :-)

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch