Re: [dpdk-dev] [PATCH v2] vhost: flush IOTLB cache on new mem table handling

[Tiwei Bie <tiwei.bie@intel.com>]

On Thu, Aug 02, 2018 at 07:21:22PM +0200, Maxime Coquelin wrote:
> IOTLB entries contain the host virtual address of the guest
> pages. When receiving a new VHOST_USER_SET_MEM_TABLE request,
> the previous regions get unmapped, so the IOTLB entries, if any,
> will be invalid. It does cause the vhost-user process to
> segfault.
> 
> This patch introduces a new function to flush the IOTLB cache,
> and call it as soon as the backend handles a VHOST_USER_SET_MEM
> request.
> 
> Fixes: 69c90e98f483 ("vhost: enable IOMMU support")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
> Changes since v1:
> - Fix indentation (Stephen)
> - Fix double iotlb-lock lock
> 
>  lib/librte_vhost/iotlb.c      | 10 ++++++++--
>  lib/librte_vhost/iotlb.h      |  2 +-
>  lib/librte_vhost/vhost_user.c |  5 +++++
>  3 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_vhost/iotlb.c b/lib/librte_vhost/iotlb.c
> index c11ebcaac..c6354fef7 100644
> --- a/lib/librte_vhost/iotlb.c
> +++ b/lib/librte_vhost/iotlb.c
> @@ -303,6 +303,13 @@ vhost_user_iotlb_cache_find(struct vhost_virtqueue *vq, uint64_t iova,
>  	return vva;
>  }
>  
> +void
> +vhost_user_iotlb_flush_all(struct vhost_virtqueue *vq)
> +{
> +	vhost_user_iotlb_cache_remove_all(vq);
> +	vhost_user_iotlb_pending_remove_all(vq);
> +}
> +
>  int
>  vhost_user_iotlb_init(struct virtio_net *dev, int vq_index)
>  {
> @@ -315,8 +322,7 @@ vhost_user_iotlb_init(struct virtio_net *dev, int vq_index)
>  		 * The cache has already been initialized,
>  		 * just drop all cached and pending entries.
>  		 */
> -		vhost_user_iotlb_cache_remove_all(vq);
> -		vhost_user_iotlb_pending_remove_all(vq);
> +		vhost_user_iotlb_flush_all(vq);
>  	}
>  
>  #ifdef RTE_LIBRTE_VHOST_NUMA
> diff --git a/lib/librte_vhost/iotlb.h b/lib/librte_vhost/iotlb.h
> index e7083e37b..60b9e4c57 100644
> --- a/lib/librte_vhost/iotlb.h
> +++ b/lib/librte_vhost/iotlb.h
> @@ -73,7 +73,7 @@ void vhost_user_iotlb_pending_insert(struct vhost_virtqueue *vq, uint64_t iova,
>  						uint8_t perm);
>  void vhost_user_iotlb_pending_remove(struct vhost_virtqueue *vq, uint64_t iova,
>  						uint64_t size, uint8_t perm);
> -
> +void vhost_user_iotlb_flush_all(struct vhost_virtqueue *vq);
>  int vhost_user_iotlb_init(struct virtio_net *dev, int vq_index);
>  
>  #endif /* _VHOST_IOTLB_H_ */
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index dc53ff712..a2d4c9ffc 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -813,6 +813,11 @@ vhost_user_set_mem_table(struct virtio_net **pdev, struct VhostUserMsg *pmsg)
>  		dev->mem = NULL;
>  	}
>  
> +	/* Flush IOTLB cache as previous HVAs are now invalid */
> +	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
> +		for (i = 0; i < dev->nr_vring; i++)
> +			vhost_user_iotlb_flush_all(dev->virtqueue[i]);

Why is the pending list also flushed?

Thanks,
Tiwei