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Date: Fri, 20 Nov 2020 09:06:53 +0100 From: Hans Verkuil <hverkuil@...all.nl> To: Daniel Vetter <daniel.vetter@...ll.ch>, DRI Development <dri-devel@...ts.freedesktop.org>, LKML <linux-kernel@...r.kernel.org> Cc: kvm@...r.kernel.org, linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, linux-media@...r.kernel.org, Tomasz Figa <tfiga@...omium.org>, Daniel Vetter <daniel.vetter@...el.com>, Jason Gunthorpe <jgg@...pe.ca>, Kees Cook <keescook@...omium.org>, Dan Williams <dan.j.williams@...el.com>, Andrew Morton <akpm@...ux-foundation.org>, John Hubbard <jhubbard@...dia.com>, Jérôme Glisse <jglisse@...hat.com>, Jan Kara <jack@...e.cz>, Pawel Osciak <pawel@...iak.com>, Marek Szyprowski <m.szyprowski@...sung.com>, Kyungmin Park <kyungmin.park@...sung.com>, Laurent Dufour <ldufour@...ux.ibm.com>, Vlastimil Babka <vbabka@...e.cz>, Daniel Jordan <daniel.m.jordan@...cle.com>, Michel Lespinasse <walken@...gle.com> Subject: Re: [PATCH v6 09/17] media/videbuf1|2: Mark follow_pfn usage as unsafe On 19/11/2020 15:41, 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"). > > Acked-by: Tomasz Figa <tfiga@...omium.org> Acked-by: Hans Verkuil <hverkuil-cisco@...all.nl> Thanks! Hans > Signed-off-by: Daniel Vetter <daniel.vetter@...el.com> > Cc: Jason Gunthorpe <jgg@...pe.ca> > Cc: Kees Cook <keescook@...omium.org> > Cc: Dan Williams <dan.j.williams@...el.com> > Cc: Andrew Morton <akpm@...ux-foundation.org> > Cc: John Hubbard <jhubbard@...dia.com> > Cc: Jérôme Glisse <jglisse@...hat.com> > Cc: Jan Kara <jack@...e.cz> > Cc: Dan Williams <dan.j.williams@...el.com> > Cc: linux-mm@...ck.org > Cc: linux-arm-kernel@...ts.infradead.org > Cc: linux-samsung-soc@...r.kernel.org > Cc: linux-media@...r.kernel.org > Cc: Pawel Osciak <pawel@...iak.com> > Cc: Marek Szyprowski <m.szyprowski@...sung.com> > Cc: Kyungmin Park <kyungmin.park@...sung.com> > Cc: Tomasz Figa <tfiga@...omium.org> > Cc: Laurent Dufour <ldufour@...ux.ibm.com> > Cc: Vlastimil Babka <vbabka@...e.cz> > Cc: Daniel Jordan <daniel.m.jordan@...cle.com> > Cc: Michel Lespinasse <walken@...gle.com> > Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch> > -- > v3: > - Reference the commit that enabled the zerocopy userptr use case to > make it abundandtly clear that this patch only affects that, and not > normal memory userptr. The old commit message already explained that > normal memory userptr is unaffected, but I guess that was not clear > enough. > --- > drivers/media/common/videobuf2/frame_vector.c | 2 +- > drivers/media/v4l2-core/videobuf-dma-contig.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c > index a0e65481a201..1a82ec13ea00 100644 > --- a/drivers/media/common/videobuf2/frame_vector.c > +++ b/drivers/media/common/videobuf2/frame_vector.c > @@ -70,7 +70,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, > break; > > while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) { > - err = follow_pfn(vma, start, &nums[ret]); > + err = unsafe_follow_pfn(vma, start, &nums[ret]); > if (err) { > if (ret == 0) > ret = err; > diff --git a/drivers/media/v4l2-core/videobuf-dma-contig.c b/drivers/media/v4l2-core/videobuf-dma-contig.c > index 52312ce2ba05..821c4a76ab96 100644 > --- a/drivers/media/v4l2-core/videobuf-dma-contig.c > +++ b/drivers/media/v4l2-core/videobuf-dma-contig.c > @@ -183,7 +183,7 @@ static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem, > user_address = untagged_baddr; > > while (pages_done < (mem->size >> PAGE_SHIFT)) { > - ret = follow_pfn(vma, user_address, &this_pfn); > + ret = unsafe_follow_pfn(vma, user_address, &this_pfn); > if (ret) > break; > >
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