Re: [RFC 0/2] Identify aliased maps in vdpa SVQ iova_tree

[Jason Wang]

On Wed, Apr 10, 2024 at 6:03 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> The guest may have overlapped memory regions, where different GPA leads
> to the same HVA.  This causes a problem when overlapped regions
> (different GPA but same translated HVA) exists in the tree, as looking
> them by HVA will return them twice.

I think I don't understand if there's any side effect for shadow virtqueue?

Thanks

>
> To solve this, track GPA in the DMA entry that acs as unique identifiers
> to the maps.  When the map needs to be removed, iova tree is able to
> find the right one.
>
> Users that does not go to this extra layer of indirection can use the
> iova tree as usual, with id = 0.
>
> This was found by Si-Wei Liu <si-wei.liu@oracle.com>, but I'm having a hard
> time to reproduce the issue.  This has been tested only without overlapping
> maps.  If it works with overlapping maps, it will be intergrated in the main
> series.
>
> Comments are welcome.  Thanks!
>
> Eugenio Pérez (2):
>   iova_tree: add an id member to DMAMap
>   vdpa: identify aliased maps in iova_tree
>
>  hw/virtio/vhost-vdpa.c   | 2 ++
>  include/qemu/iova-tree.h | 5 +++--
>  util/iova-tree.c         | 3 ++-
>  3 files changed, 7 insertions(+), 3 deletions(-)
>
> --
> 2.44.0
>