On Tue, Dec 25, 2012 at 01:08:40PM +0900, Takuya Yoshikawa wrote: > On Mon, 24 Dec 2012 15:27:17 +0200 > Gleb Natapov <gleb@xxxxxxxxxx> wrote: > > > > @@ -6897,7 +6897,14 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, > > > spin_lock(&kvm->mmu_lock); > > > if (nr_mmu_pages) > > > kvm_mmu_change_mmu_pages(kvm, nr_mmu_pages); > > > - kvm_mmu_slot_remove_write_access(kvm, mem->slot); > > > + /* > > > + * Write protect all pages for dirty logging. > > > + * Existing largepage mappings are destroyed here and new ones will > > > + * not be created until the end of the logging. > > > + */ > > > + if ((mem->flags & KVM_MEM_LOG_DIRTY_PAGES) && > > > + !(old.flags & KVM_MEM_LOG_DIRTY_PAGES)) > > > + kvm_mmu_slot_remove_write_access(kvm, mem->slot); > > We should not check old slot flags here or at least check that > > old.npages is not zero. Userspace may delete a slot using old flags, > > then, if new memslot is created with dirty log enabled, it will not be > > protected. > > The flag, KVM_MEM_LOG_DIRTY_PAGES, is explicitely cleared when we > delete a slot to free dirty_bitmap: > > if (!npages) > mem->flags &= ~KVM_MEM_LOG_DIRTY_PAGES; > > So when old.npages is not zero, the second condition must be true. > Right. I was looking for where it is cleared and missed that. > Other parts are doing "if (!slot->dirty_bitmap)" to see if the slot > is in dirty logging mode. If you prefer, we can do the same here. > Does not matter to me. If you think it will be more consistent do it. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
