Re: [Qemu-devel] [PATCH V3 2/3] virtio: destroy region cache during reset

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Tue, 14 Mar 2017 11:01:41 +0800
Jason Wang <jasowang@redhat.com> wrote:

> We don't destroy region cache during reset which can make the maps
> of previous driver leaked to a buggy or malicious driver that don't
> set vring address before starting to use the device. Fix this by
> destroy the region cache during reset and validate it before trying to
> see them.
> 
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> Changes from V2:
> - introduce a helper and assert caches != NULL
> Changes from v1:
> - switch to use rcu in virtio_virtqueue_region_cache()
> - use unlikely() when needed
> ---
>  hw/virtio/virtio.c | 46 ++++++++++++++++++++++++++++++----------------
>  1 file changed, 30 insertions(+), 16 deletions(-)
> 

> @@ -249,11 +255,10 @@ static inline void vring_used_idx_set(VirtQueue *vq, uint16_t val)
>  /* Called within rcu_read_lock().  */
>  static inline void vring_used_flags_set_bit(VirtQueue *vq, int mask)
>  {
> -    VRingMemoryRegionCaches *caches = atomic_rcu_read(&vq->vring.caches);
> +    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
>      VirtIODevice *vdev = vq->vdev;
>      hwaddr pa = offsetof(VRingUsed, flags);
>      uint16_t flags = virtio_lduw_phys_cached(vq->vdev, &caches->used, pa);
> -

Unrelated whitespace change.

>      virtio_stw_phys_cached(vdev, &caches->used, pa, flags | mask);
>      address_space_cache_invalidate(&caches->used, pa, sizeof(flags));
>  }

Other than that:

Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>