From: Christoph Hellwig <hch@infradead.org>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: DRI Development <dri-devel@lists.freedesktop.org>,
LKML <linux-kernel@vger.kernel.org>,
kvm@vger.kernel.org, linux-mm@kvack.org,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
Tomasz Figa <tfiga@chromium.org>,
Hans Verkuil <hverkuil-cisco@xs4all.nl>,
Daniel Vetter <daniel.vetter@intel.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Kees Cook <keescook@chromium.org>,
Dan Williams <dan.j.williams@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
John Hubbard <jhubbard@nvidia.com>,
J??r??me Glisse <jglisse@redhat.com>, Jan Kara <jack@suse.cz>,
Pawel Osciak <pawel@osciak.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
Laurent Dufour <ldufour@linux.ibm.com>,
Vlastimil Babka <vbabka@suse.cz>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
Michel Lespinasse <walken@google.com>
Subject: Re: [PATCH 2/3] media/videobuf1|2: Mark follow_pfn usage as unsafe
Date: Tue, 16 Mar 2021 15:45:49 +0000 [thread overview]
Message-ID: <20210316154549.GA60450@infradead.org> (raw)
In-Reply-To: <20210316153303.3216674-3-daniel.vetter@ffwll.ch>
On Tue, Mar 16, 2021 at 04:33:02PM +0100, Daniel Vetter wrote:
> The media model assumes that buffers are all preallocated, so that
> when a media pipeline is running we never miss a deadline because the
> buffers aren't allocated or available.
>
> This means we cannot fix the v4l follow_pfn usage through
> mmu_notifier, without breaking how this all works. The only real fix
> is to deprecate userptr support for VM_IO | VM_PFNMAP mappings and
> tell everyone to cut over to dma-buf memory sharing for zerocopy.
>
> userptr for normal memory will keep working as-is, this only affects
> the zerocopy userptr usage enabled in 50ac952d2263 ("[media]
> videobuf2-dma-sg: Support io userptr operations on io memory").
Maybe I'm missing something, but wasn't the conclusion last time that
this hackish early device to device copy support can just go away?
next prev parent reply other threads:[~2021-03-16 15:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 15:33 [PATCH 0/3] switch to unsafe_follow_pfn Daniel Vetter
2021-03-16 15:33 ` [PATCH 1/3] mm: Add unsafe_follow_pfn Daniel Vetter
2021-03-29 13:29 ` Jason Gunthorpe
2021-03-16 15:33 ` [PATCH 2/3] media/videobuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2021-03-16 15:45 ` Christoph Hellwig [this message]
2021-03-16 15:52 ` Daniel Vetter
2021-03-17 7:22 ` Christoph Hellwig
2021-03-17 8:04 ` Daniel Vetter
2021-03-16 15:33 ` [PATCH 3/3] mm: unexport follow_pfn Daniel Vetter
2021-03-24 12:52 ` Jason Gunthorpe
2021-03-24 14:31 ` Paolo Bonzini
2021-03-24 19:17 ` Daniel Vetter
2021-03-25 21:33 ` Daniel Vetter
2021-03-29 13:31 ` Jason Gunthorpe
2021-04-08 10:05 ` Daniel Vetter
2021-04-08 11:40 ` Paolo Bonzini
2021-04-08 11:44 ` Daniel Vetter
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