On Sun 24-06-18 10:11:21, Paolo Bonzini wrote: > On 22/06/2018 17:02, Michal Hocko wrote: > > @@ -7215,6 +7216,8 @@ void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm, > > apic_address = gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT); > > if (start <= apic_address && apic_address < end) > > kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD); > > + > > + return 0; > > This is wrong, gfn_to_hva can sleep. Hmm, I have tried to crawl the call chain and haven't found any sleepable locks taken. Maybe I am just missing something. __kvm_memslots has a complex locking assert. I do not see we would take slots_lock anywhere from the notifier call path. IIUC that means that users_count has to be zero at that time. I have no idea how that is guaranteed. > You could do the the kvm_make_all_cpus_request unconditionally, but only > if !blockable is a really rare thing. OOM would be fine, since the > request actually would never be processed, but I'm afraid of more uses > of !blockable being introduced later. Well, if this is not generally guaranteed then I have to come up with a different flag. E.g. OOM_CONTEXT that would be more specific to contrains for the callback. -- Michal Hocko SUSE Labs
