Il 03/07/2013 10:18, Takuya Yoshikawa ha scritto:
> Since kvm_arch_prepare_memory_region() is called right after installing
> the slot marked invalid, wraparound checking should be there to avoid
> zapping mmio sptes when mmio generation is still MMIO_MAX_GEN - 1.
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@xxxxxxxxxxxxx>
> ---
> This seems to be the simplest solution for fixing the off-by-one issue
> we discussed before.
>
> arch/x86/kvm/mmu.c | 5 +----
> arch/x86/kvm/x86.c | 7 +++++++
> 2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 0d094da..bf7af1e 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -4383,11 +4383,8 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
> /*
> * The very rare case: if the generation-number is round,
> * zap all shadow pages.
> - *
> - * The max value is MMIO_MAX_GEN - 1 since it is not called
> - * when mark memslot invalid.
> */
> - if (unlikely(kvm_current_mmio_generation(kvm) >= (MMIO_MAX_GEN - 1))) {
> + if (unlikely(kvm_current_mmio_generation(kvm) >= MMIO_MAX_GEN)) {
> printk_ratelimited(KERN_INFO "kvm: zapping shadow pages for mmio generation wraparound\n");
> kvm_mmu_invalidate_zap_all_pages(kvm);
> }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 7d71c0f..9ddd4ff 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7046,6 +7046,13 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
> memslot->userspace_addr = userspace_addr;
> }
>
> + /*
> + * In these cases, slots->generation has been increased for marking the
> + * slot invalid, so we need wraparound checking here.
> + */
> + if ((change == KVM_MR_DELETE) || (change == KVM_MR_MOVE))
> + kvm_mmu_invalidate_mmio_sptes(kvm);
> +
> return 0;
> }
>
>
Applied, thanks.
Paolo
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