Em Fri, 9 Oct 2020 09:59:27 +0200
Daniel Vetter escreveu:
> 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.
I won't repeat here the discussions for patch 09/17, but
just to be clear about this one:
NACK.
We need a better alternative to avoid breaking existing
media applications.
>
> Signed-off-by: Daniel Vetter
> Cc: Jason Gunthorpe
> Cc: Kees Cook
> Cc: Dan Williams
> Cc: Andrew Morton
> Cc: John Hubbard
> Cc: Jérôme Glisse
> Cc: Jan Kara
> Cc: Dan Williams
> Cc: linux...@kvack.org
> Cc: linux-arm-ker...@lists.infradead.org
> Cc: linux-samsung-...@vger.kernel.org
> Cc: linux-me...@vger.kernel.org
> Cc: Pawel Osciak
> Cc: Marek Szyprowski
> Cc: Kyungmin Park
> Cc: Tomasz Figa
> Cc: Laurent Dufour
> Cc: Vlastimil Babka
> Cc: Daniel Jordan
> Cc: Michel Lespinasse
> ---
> 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 2b0b97761d15..a1b85fe9e7c1 100644
> --- a/drivers/media/common/videobuf2/frame_vector.c
> +++ b/drivers/media/common/videobuf2/frame_vector.c
> @@ -69,7 +69,7 @@ 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, [ret]);
> + err = unsafe_follow_pfn(vma, start, [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, _pfn);
> + ret = unsafe_follow_pfn(vma, user_address, _pfn);
> if (ret)
> break;
>
Thanks,
Mauro
