On 25/06/2018 10:45, Michal Hocko wrote: > On Mon 25-06-18 10:10:18, Paolo Bonzini wrote: >> On 25/06/2018 09:57, Michal Hocko wrote: >>> 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. >> >> Nevermind, ENOCOFFEE. This is gfn_to_hva, not gfn_to_pfn. It only >> needs SRCU. > > OK, so just the make sure I follow, the change above is correct? Yes. It's only gfn_to_pfn that calls get_user_pages and therefore can sleep. Thanks, Paolo
