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From: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
	"Tomasz Figa" <tfiga@chromium.org>,
	linux-s390 <linux-s390@vger.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	"Jan Kara" <jack@suse.cz>, "Kees Cook" <keescook@chromium.org>,
	"KVM list" <kvm@vger.kernel.org>, "Linux MM" <linux-mm@kvack.org>,
	"John Hubbard" <jhubbard@nvidia.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
	"open list:DMA BUFFER SHARING FRAMEWORK"
	<linux-media@vger.kernel.org>,
	"Hans Verkuil" <hverkuil@xs4all.nl>,
	"Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Subject: Re: [PATCH v2 09/17] mm: Add unsafe_follow_pfn
Date: Sun, 11 Oct 2020 08:27:41 +0200
Message-ID: <20201011082741.6bed4d71@coco.lan> (raw)
In-Reply-To: <CAKMK7uGhq+BiaJ5jD+bkO4VOaCPuUZ_empA3Ojr1AsvwNef6QQ@mail.gmail.com>

Em Sat, 10 Oct 2020 23:50:27 +0200
Daniel Vetter <daniel.vetter@ffwll.ch> escreveu:

> On Sat, Oct 10, 2020 at 11:36 PM Laurent Pinchart
> <laurent.pinchart@ideasonboard.com> wrote:
> >

> > > We probably still have a few legacy drivers using videobuf (non-2),
> > > but IMHO those should be safe to put behind some disabled-by-default
> > > Kconfig symbol or even completely drop, as the legacy framework has
> > > been deprecated for many years already.  
> >
> > There's 8 drivers left, and they support a very large number of devices.
> > I expect unhappy users distros stop shipping them. On the other hand,
> > videobuf has been deprecated for a loooooooong time, so there has been
> > plenty of time to convert the remaining drivers to videobuf2. If nobody
> > can do it, then we'll have to drop support for these devices given the
> > security issues.  
> 
> Again, the issue here is _only_ with follow_pfn. For videobuf1 this
> means videbuf-dma-contig.c userptr support is broken. Unlike videobuf2
> it means it's broken for all usage (not just zero-copy userptr),
> because videbuf-dma-contig.c lacks the pin_user_pages path.

Well, follow_pfn() is used only by videbuf-dma-contig.c. If this is 
the only part of VB1 that will have userptr broken, then there's
just one driver that might be affected: davinci.

Yet, taking a deeper look:

	$ git grep include drivers/media/platform/davinci/|grep -i videobuf
	drivers/media/platform/davinci/vpif_capture.h:#include <media/videobuf2-dma-contig.h>
	drivers/media/platform/davinci/vpif_display.h:#include <media/videobuf2-dma-contig.h>

It sounds to me that it was already converted to VB2, but some VB1
symbols were not converted at its Kconfig.

It sounds to me that there are other drivers with some VB1 left overs
at Kconfig, as those are the only ones using VB1 those days:

	$ for i in $(git grep media/videobuf drivers |grep -v videobuf2 |grep -v v4l2-core|cut -d: -f1); do dirname $i; done|sort|uniq
	drivers/media/pci/bt8xx
	drivers/media/pci/cx18
	drivers/media/platform
	drivers/media/usb/tm6000
	drivers/media/usb/zr364xx
	drivers/staging/media/atomisp/pci

> But that
> would be easy to add if this poses a  problem I think - we just need
> to carry over the pin_user_pages_fast logic from videbuf2, no driver
> changes required. But of course I don't think we should do that before
> someone reports the regression, since videobuf1 userptr is doubly
> deprecated :-)

I think otherwise. Keeping a broken component at the Kernel is 
a bad idea. 

Yet, from my quick search above, it sounds to me that it is time for 
us to retire the VB1 DMA contig support as a hole, as there's no client 
for it anymore.

I'll work on some patches cleaning up the VB1 left overs at
Kconfig and removing videbuf-dma-contig.c for good, if there's
no hidden dependency on it.


Thanks,
Mauro

  reply index

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09  7:59 [PATCH v2 00/17] follow_pfn and other iomap races Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 01/17] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-10-16  7:42   ` John Hubbard
2020-10-09  7:59 ` [PATCH v2 02/17] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 03/17] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-10-10 20:26   ` Oded Gabbay
2020-10-10 21:32     ` Daniel Vetter
2020-10-10 21:41       ` Daniel Vetter
2020-10-10 21:47         ` Oded Gabbay
2020-10-16  7:45   ` John Hubbard
2020-10-09  7:59 ` [PATCH v2 04/17] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 05/17] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-10-16  7:54   ` John Hubbard
2020-10-16  8:03     ` Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 06/17] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-10-09 10:14   ` Mauro Carvalho Chehab
2020-10-09 16:57     ` Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 07/17] mm: Close race in generic_access_phys Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 08/17] s390/pci: Remove races against pte updates Daniel Vetter
2020-10-12 14:03   ` Niklas Schnelle
2020-10-12 14:19     ` Daniel Vetter
2020-10-12 14:39       ` Niklas Schnelle
2020-10-21  7:55       ` Niklas Schnelle
2020-10-22  7:39         ` Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 09/17] mm: Add unsafe_follow_pfn Daniel Vetter
2020-10-09 10:34   ` Mauro Carvalho Chehab
2020-10-09 12:21     ` Jason Gunthorpe
2020-10-09 12:37       ` Mauro Carvalho Chehab
2020-10-09 12:39         ` Mauro Carvalho Chehab
2020-10-09 12:48         ` Jason Gunthorpe
2020-10-09 17:52           ` Daniel Vetter
2020-10-09 18:01             ` Jason Gunthorpe
2020-10-09 19:31               ` Daniel Vetter
2020-10-10  9:21             ` Mauro Carvalho Chehab
2020-10-10 10:53               ` Daniel Vetter
2020-10-10 11:39                 ` Mauro Carvalho Chehab
2020-10-10 11:56                   ` Daniel Vetter
2020-10-10 17:22             ` Tomasz Figa
2020-10-10 21:35               ` Laurent Pinchart
2020-10-10 21:50                 ` Daniel Vetter
2020-10-11  6:27                   ` Mauro Carvalho Chehab [this message]
2020-10-11  6:36                     ` Mauro Carvalho Chehab
2020-10-10 21:11             ` Laurent Pinchart
2020-10-12 10:46           ` Marek Szyprowski
2020-10-12 13:49             ` Daniel Vetter
2020-10-10 17:30         ` Tomasz Figa
2020-10-09  7:59 ` [PATCH v2 10/17] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-10-10  9:24   ` Mauro Carvalho Chehab
2020-10-09  7:59 ` [PATCH v2 11/17] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 12/17] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 13/17] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 14/17] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-10-09 10:59   ` Greg Kroah-Hartman
2020-10-09 12:31   ` Jason Gunthorpe
2020-10-09 14:24     ` Daniel Vetter
2020-10-09 14:32       ` Jason Gunthorpe
2020-10-09 18:28         ` Dan Williams
2020-10-15  0:09           ` Jason Gunthorpe
2020-10-15  7:52             ` Daniel Vetter
2020-10-15  7:55               ` Daniel Vetter
2020-10-15 15:29             ` Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 15/17] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-10-09 10:58   ` Greg Kroah-Hartman
2020-10-09  7:59 ` [PATCH v2 16/17] PCI: Revoke mappings like devmem Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 17/17] drm/i915: Properly request PCI BARs Daniel Vetter
2020-10-09  9:47   ` Ville Syrjälä
2020-10-09 10:01     ` Daniel Vetter
2020-10-09 10:41       ` Ville Syrjälä
2020-10-09 14:18         ` Daniel Vetter

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