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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 08:36:42 +0200
Message-ID: <20201011083642.06ea8062@coco.lan> (raw)
In-Reply-To: <20201011082741.6bed4d71@coco.lan>

Em Sun, 11 Oct 2020 08:27:41 +0200
Mauro Carvalho Chehab <mchehab+huawei@kernel.org> escreveu:

> 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

This is incomplete. There are two drivers that include videobuf
indirectly:

	include/media/davinci/vpfe_capture.h
	include/media/drv-intf/saa7146_vv.h

I double-checked that DaVinci still uses VB1. There are 
actually two clients for videbuf-dma-contig.c: davinci and fsl-viu.

Those two will be affected, if we don't add pin_user_pages_fast()
support to VB1 or convert them to VB2.

> 
> > 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



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
2020-10-11  6:36                     ` Mauro Carvalho Chehab [this message]
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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