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From: Hans Verkuil <hverkuil@xs4all.nl>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>
Cc: linux-samsung-soc@vger.kernel.org, "Jan Kara" <jack@suse.cz>,
	"Kees Cook" <keescook@chromium.org>,
	kvm@vger.kernel.org, "Jason Gunthorpe" <jgg@ziepe.ca>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Kyungmin Park" <kyungmin.park@samsung.com>,
	"Daniel Jordan" <daniel.m.jordan@oracle.com>,
	"Tomasz Figa" <tfiga@chromium.org>,
	linux-mm@kvack.org, "Jérôme Glisse" <jglisse@redhat.com>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Pawel Osciak" <pawel@osciak.com>,
	"Michel Lespinasse" <walken@google.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Marek Szyprowski" <m.szyprowski@samsung.com>,
	"Laurent Dufour" <ldufour@linux.ibm.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-media@vger.kernel.org
Subject: Re: [PATCH v6 09/17] media/videbuf1|2: Mark follow_pfn usage as unsafe
Date: Fri, 20 Nov 2020 09:06:53 +0100
Message-ID: <f1f3a1d8-d62a-6e93-afc1-87a8e51081e9@xs4all.nl> (raw)
In-Reply-To: <20201119144146.1045202-10-daniel.vetter@ffwll.ch>

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@chromium.org>

Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Thanks!

	Hans

> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Jérôme Glisse <jglisse@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Dan Williams <dan.j.williams@intel.com>
> 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 <pawel@osciak.com>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Tomasz Figa <tfiga@chromium.org>
> Cc: Laurent Dufour <ldufour@linux.ibm.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
> Cc: Michel Lespinasse <walken@google.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.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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  reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-19 14:41 [PATCH v6 00/17] follow_pfn and other iomap races Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 01/17] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 02/17] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 03/17] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-11-21 12:47   ` Oded Gabbay
2020-11-19 14:41 ` [PATCH v6 04/17] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-11-21 10:15   ` Oded Gabbay
2020-11-19 14:41 ` [PATCH v6 05/17] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 06/17] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-11-20  8:07   ` Hans Verkuil
2020-11-19 14:41 ` [PATCH v6 07/17] mm: Close race in generic_access_phys Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 08/17] mm: Add unsafe_follow_pfn Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 09/17] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-11-20  8:06   ` Hans Verkuil [this message]
2020-11-20  8:28     ` Hans Verkuil
2020-11-20  8:32       ` Tomasz Figa
2020-11-20  9:18       ` Daniel Vetter
2020-11-20 10:38         ` Hans Verkuil
2020-11-20 10:51           ` Daniel Vetter
2020-11-20 12:08             ` Hans Verkuil
2020-11-20 12:23               ` Tomasz Figa
2020-11-24 14:16                 ` Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 10/17] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 11/17] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 12/17] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 13/17] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 14/17] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 15/17] PCI: Revoke mappings like devmem Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 16/17] RFC: kvm: pass kvm argument to follow_pfn callsites Daniel Vetter
2020-11-20 15:33   ` Paolo Bonzini
2020-11-20 15:44     ` Daniel Vetter
2020-11-20 15:55       ` Paolo Bonzini
2020-11-19 14:41 ` [PATCH v6 17/17] RFC: mm: add mmu_notifier argument to follow_pfn Daniel Vetter
2020-11-20 18:30   ` Jason Gunthorpe
2020-11-24 14:28     ` Daniel Vetter
2020-11-24 15:55       ` Jason Gunthorpe
2020-11-25  9:00         ` Daniel Vetter
2020-11-27 13:12 ` [PATCH v6 00/17] follow_pfn and other iomap races Jason Gunthorpe
2020-11-27 15:36   ` Daniel Vetter

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