From: Jason Gunthorpe <jgg@ziepe.ca>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "DRI Development" <dri-devel@lists.freedesktop.org>,
LKML <linux-kernel@vger.kernel.org>,
"KVM list" <kvm@vger.kernel.org>, "Linux MM" <linux-mm@kvack.org>,
"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
"open list:DMA BUFFER SHARING FRAMEWORK"
<linux-media@vger.kernel.org>,
linux-s390 <linux-s390@vger.kernel.org>,
"Daniel Vetter" <daniel.vetter@intel.com>,
"Kees Cook" <keescook@chromium.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"John Hubbard" <jhubbard@nvidia.com>,
"Jérôme Glisse" <jglisse@redhat.com>, "Jan Kara" <jack@suse.cz>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Linux PCI" <linux-pci@vger.kernel.org>,
"Daniel Vetter" <daniel.vetter@ffwll.com>
Subject: Re: [PATCH v3 12/16] PCI: Obey iomem restrictions for procfs mmap
Date: Wed, 21 Oct 2020 12:13:52 -0300 [thread overview]
Message-ID: <20201021151352.GL36674@ziepe.ca> (raw)
In-Reply-To: <CAKMK7uEWe8CaT7zjcZ6dJAKHxtxtqzjVB35fCFviwhcnqksDfw@mail.gmail.com>
On Wed, Oct 21, 2020 at 04:42:11PM +0200, Daniel Vetter wrote:
> Uh yes. In drivers/gpu this isn't a problem because we only install
> ptes from the vm_ops->fault handler. So no races. And I don't think
> you can fix this otherwise through holding locks: mmap_sem we can't
> hold because before vma_link we don't even know which mm_struct is
> involved, so can't solve the race. Plus this would be worse that
> mm_take_all_locks used by mmu notifier. And the address_space
> i_mmap_lock is also no good since it's not held during the ->mmap
> callback, when we write the ptes. And the resource locks is even less
> useful, since we're not going to hold that at vma_link() time for
> sure.
>
> Hence delaying the pte writes after the vma_link, which means ->fault
> time, looks like the only way to close this gap.
> Trouble is I have no idea how to do this cleanly ...
How about add a vm_ops callback 'install_pages'/'prefault_pages' ?
Call it after vm_link() - basically just move the remap_pfn, under
some other lock, into there.
Jason
next prev parent reply other threads:[~2020-10-21 15:14 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-21 8:56 [PATCH v3 00/16] follow_pfn and other iomap races Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 01/16] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 02/16] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 03/16] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 04/16] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-10-23 9:12 ` Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 05/16] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 06/16] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 07/16] mm: Close race in generic_access_phys Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 08/16] s390/pci: Remove races against pte updates Daniel Vetter
2020-10-21 9:37 ` Niklas Schnelle
2020-10-21 13:56 ` Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 09/16] mm: Add unsafe_follow_pfn Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 10/16] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 11/16] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 12/16] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-10-21 12:50 ` Jason Gunthorpe
2020-10-21 14:42 ` Daniel Vetter
2020-10-21 15:13 ` Jason Gunthorpe [this message]
2020-10-21 15:54 ` Daniel Vetter
2020-10-21 16:37 ` Jason Gunthorpe
2020-10-21 19:24 ` Daniel Vetter
2020-10-21 23:20 ` Jason Gunthorpe
2020-10-22 7:00 ` Daniel Vetter
2020-10-22 11:43 ` Jason Gunthorpe
2020-10-22 13:04 ` Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 13/16] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-10-21 18:21 ` Dan Williams
2020-10-21 8:56 ` [PATCH v3 14/16] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-10-21 18:59 ` Dan Williams
2020-10-21 19:25 ` Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 15/16] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-10-21 8:56 ` [PATCH v3 16/16] PCI: Revoke mappings like devmem Daniel Vetter
2020-10-21 12:51 ` [PATCH v3 00/16] follow_pfn and other iomap races Jason Gunthorpe
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