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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 > 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 > Cc: Paolo Bonzini > Cc: Jason Gunthorpe > Cc: Cornelia Huck > Cc: Peter Xu > Cc: Alex Williamson > 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 > --- > include/linux/mm.h | 2 -- > mm/memory.c | 26 +++++--------------------- > mm/nommu.c | 13 +------------ > 3 files changed, 6 insertions(+), 35 deletions(-) I think this is the right thing to do. Alex is working on fixing VFIO and while kvm is still racy using follow pte, I think they are working on it too? Jason _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel