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 <yoshikawa_takuya...@lab.ntt.co.jp>
> ---
> 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.
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