On Wed, Nov 6, 2019 at 3:39 PM Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote: > > On Wed, Nov 06, 2019 at 03:20:11PM -0800, Dan Williams wrote: > > After some more thought I'd feel more comfortable just collapsing the > > ZONE_DEVICE case into the VM_IO/VM_PFNMAP case. I.e. with something > > like this (untested) that just drops the reference immediately and let > > kvm_is_reserved_pfn() do the right thing going forward. > > This will break the page fault flow, as it will allow the page to be > whacked before KVM can ensure it will get proper notification from the > mmu_notifier. E.g. KVM would install the PFN in its secondary MMU after > getting the invalidate notification for the PFN. How do mmu notifiers get held off by page references and does that machinery work with ZONE_DEVICE? Why is this not a concern for the VM_IO and VM_PFNMAP case?
