Re: [PATCH v2] hw/virtio/vhost-shadow-virtqueue: range boundary in translation

On 2026/08/18 8:31, Connor Kite wrote:
> iova-tree expects inclusive range sizing when maps are allocated or searched.
> Currently, svqs use exclusive sizing when searching their
> vhost-iova-tree for a match to the region to be translated.  This could
> lead to errors if the region to be translated is at the edge of an iova
> region.
> 
> Fix this by reducing `needle.size` by 1 in
> vhost_svq_translate_addr to bring it in line with DMAMap and iova-tree
> convention.
> 
> The only current user of svq->iova_tree is hw/virtio/vhost-vdpa.c, which
> also treats size as inclusive when using the tree API.  In progress work
> on vhost-user isolation mode in hw/virtio.vhost-vdpa.c also uses
> inclusive sizing when interacting with the tree.

Please correct hw/virtio.vhost-vdpa.c to hw/virtio/vhost-user.c. The 
former does not exist and misidentifies where the vhost-user isolation 
work lives.

> 
> This patch is an updated version of one from the patch series "vhost-user:
> isolated memory".  The patch has been isolated from the series as it
> is not tightly coupled with the rest of the series.
> 
> Signed-off-by: Connor Kite <[email protected]>
> Reviewed-by: Stefan Hajnoczi <[email protected]>

Please add the required trailer:

     Fixes: 34e3c94edaef ("vdpa: Add custom IOTLB translations to SVQ").

That commit introduced the oversized needle, and QEMU policy requests a
Fixes: trailer for in-tree regressions.

Regards,
Akihiko Odaki

> ---
> V2 Differences:
> - Context added about users of svq->iova_tree and their adoption of
>    inclusive sizing
> 
>   hw/virtio/vhost-shadow-virtqueue.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
> index bcb7f2ffc7..c8831d52be 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -99,19 +99,25 @@ static bool vhost_svq_translate_addr(const VhostShadowVirtqueue *svq,
>           const DMAMap *map;
>           DMAMap needle;
>   
> +        if (unlikely(iovec[i].iov_len == 0)) {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "Zero-sized buffer made available by guest");
> +            return false;
> +        }
> +
>           /* Check if the descriptor is backed by guest memory  */
>           if (gpas) {
>               /* Search the GPA->IOVA tree */
>               needle = (DMAMap) {
>                   .translated_addr = gpas[i],
> -                .size = iovec[i].iov_len,
> +                .size = iovec[i].iov_len - 1,  /* Inclusive */
>               };
>               map = vhost_iova_tree_find_gpa(svq->iova_tree, &needle);
>           } else {
>               /* Search the IOVA->HVA tree */
>               needle = (DMAMap) {
>                   .translated_addr = (hwaddr)(uintptr_t)iovec[i].iov_base,
> -                .size = iovec[i].iov_len,
> +                .size = iovec[i].iov_len - 1, /* Inclusive */
>               };
>               map = vhost_iova_tree_find_iova(svq->iova_tree, &needle);
>           }