From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH 1/7] KVM: Write protect the updated slot only when we start dirty logging Date: Mon, 24 Dec 2012 15:27:17 +0200 Message-ID: <20121224132717.GW17584@redhat.com> References: <20121218162558.65a8bfd3.yoshikawa_takuya_b1@lab.ntt.co.jp> <20121218162647.009f468e.yoshikawa_takuya_b1@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Takuya Yoshikawa Return-path: Content-Disposition: inline In-Reply-To: <20121218162647.009f468e.yoshikawa_takuya_b1@lab.ntt.co.jp> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, Dec 18, 2012 at 04:26:47PM +0900, Takuya Yoshikawa wrote: > This is needed to make kvm_mmu_slot_remove_write_access() rmap based: > otherwise we may end up using invalid rmap's. > > Signed-off-by: Takuya Yoshikawa > --- > arch/x86/kvm/x86.c | 9 ++++++++- > virt/kvm/kvm_main.c | 1 - > 2 files changed, 8 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 1c9c834..9451efa 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -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. > spin_unlock(&kvm->mmu_lock); > /* > * If memory slot is created, or moved, we need to clear all > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index bd31096..0ef5daa 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -805,7 +805,6 @@ int __kvm_set_memory_region(struct kvm *kvm, > if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) { > if (kvm_create_dirty_bitmap(&new) < 0) > goto out_free; > - /* destroy any largepage mappings for dirty tracking */ > } > > if (!npages || base_gfn != old.base_gfn) { > -- > 1.7.5.4 -- Gleb.