Messages in this thread | | | Date | Thu, 8 Apr 2021 12:05:13 +0200 | From | Daniel Vetter <> | Subject | Re: [PATCH 3/3] mm: unexport follow_pfn |
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On Mon, Mar 29, 2021 at 10:31:01AM -0300, Jason Gunthorpe wrote: > On Tue, Mar 16, 2021 at 04:33:03PM +0100, Daniel Vetter wrote: > > Both kvm (in bd2fae8da794 ("KVM: do not assume PTE is writable after > > follow_pfn")) and vfio (in 07956b6269d3 ("vfio/type1: Use > > follow_pte()")) have lost their callsites of follow_pfn(). All the > > other ones have been switched over to unsafe_follow_pfn because they > > cannot be fixed without breaking userspace api. > > > > Argueably the vfio code is still racy, but that's kinda a bigger > > vfio and kvm
Hm I thought kvm is non-racy due to the mmu notifier catch races?
> > > picture. But since it does leak the pte beyond where it drops the pt > > lock, without anything else like an mmu notifier guaranteeing > > coherence, the problem is at least clearly visible in the vfio code. > > So good enough with me. > > > > I've decided to keep the explanation that after dropping the pt lock > > you must have an mmu notifier if you keep using the pte somehow by > > adjusting it and moving it into the kerneldoc for the new follow_pte() > > function. > > > > Cc: 3pvd@google.com > > Cc: Jann Horn <jannh@google.com> > > Cc: Paolo Bonzini <pbonzini@redhat.com> > > Cc: Jason Gunthorpe <jgg@nvidia.com> > > Cc: Cornelia Huck <cohuck@redhat.com> > > Cc: Peter Xu <peterx@redhat.com> > > Cc: Alex Williamson <alex.williamson@redhat.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: kvm@vger.kernel.org > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> > > --- > > include/linux/mm.h | 2 -- > > mm/memory.c | 26 +++++--------------------- > > mm/nommu.c | 13 +------------ > > 3 files changed, 6 insertions(+), 35 deletions(-) > > Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Thanks for your r-b tags, I'll add them. -Daniel
> > Jason
-- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
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