From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sat, 10 Oct 2020 11:24:16 +0200 From: Mauro Carvalho Chehab Subject: Re: [PATCH v2 10/17] media/videbuf1|2: Mark follow_pfn usage as unsafe Message-ID: <20201010112416.4259249a@coco.lan> In-Reply-To: <20201009075934.3509076-11-daniel.vetter@ffwll.ch> References: <20201009075934.3509076-1-daniel.vetter@ffwll.ch> <20201009075934.3509076-11-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable List-ID: To: Daniel Vetter , Linus Torvalds Cc: DRI Development , LKML , 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, linux-s390@vger.kernel.org, Daniel Vetter , Jason Gunthorpe , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , =?UTF-8?B?SsOpcsO0bWU=?= Glisse , Jan Kara , Pawel Osciak , Marek Szyprowski , Kyungmin Park , Tomasz Figa , Laurent Dufour , Vlastimil Babka , Daniel Jordan , Michel Lespinasse 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. >=20 > 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. >=20 > 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. >=20 > Signed-off-by: Daniel Vetter > Cc: Jason Gunthorpe > Cc: Kees Cook > Cc: Dan Williams > Cc: Andrew Morton > Cc: John Hubbard > Cc: J=C3=A9r=C3=B4me Glisse > Cc: Jan Kara > Cc: Dan Williams > Cc: linux-mm@kvack.org > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-samsung-soc@vger.kernel.org > Cc: linux-media@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(-) >=20 > diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/medi= a/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; > =20 > while (ret < nr_frames && start + PAGE_SIZE <=3D vma->vm_end) { > - err =3D follow_pfn(vma, start, &nums[ret]); > + err =3D unsafe_follow_pfn(vma, start, &nums[ret]); > if (err) { > if (ret =3D=3D 0) > ret =3D err; > diff --git a/drivers/media/v4l2-core/videobuf-dma-contig.c b/drivers/medi= a/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 videob= uf_dma_contig_memory *mem, > user_address =3D untagged_baddr; > =20 > while (pages_done < (mem->size >> PAGE_SHIFT)) { > - ret =3D follow_pfn(vma, user_address, &this_pfn); > + ret =3D unsafe_follow_pfn(vma, user_address, &this_pfn); > if (ret) > break; > =20 Thanks, Mauro