[RFC 03/27] vhost: fix IOTLB entries overlap check with previous entry

[Mike Pattrick]

On Fri, Mar 31, 2023 at 11:43 AM Maxime Coquelin
<maxime.coquelin at redhat.com> wrote:
>
> Commit 22b6d0ac691a ("vhost: fix madvise IOTLB entries pages overlap check")
> fixed the check to ensure the entry to be removed does not
> overlap with the next one in the IOTLB cache before marking
> it as DONTDUMP with madvise(). This is not enough, because
> the same issue is present when comparing with the previous
> entry in the cache, where the end address of the previous
> entry should be used, not the start one.
>
> Fixes: dea092d0addb ("vhost: fix madvise arguments alignment")
> Cc: stable at dpdk.org
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>

Hi Maxime,

This makes sense.

Acked-by: Mike Pattrick <mkp at redhat.com>

> ---
>  lib/vhost/iotlb.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/lib/vhost/iotlb.c b/lib/vhost/iotlb.c
> index 3f45bc6061..870c8acb88 100644
> --- a/lib/vhost/iotlb.c
> +++ b/lib/vhost/iotlb.c
> @@ -178,8 +178,8 @@ vhost_user_iotlb_cache_random_evict(struct virtio_net *dev, struct vhost_virtque
>                         mask = ~(alignment - 1);
>
>                         /* Don't disable coredump if the previous node is in the same page */
> -                       if (prev_node == NULL ||
> -                                       (node->uaddr & mask) != (prev_node->uaddr & mask)) {
> +                       if (prev_node == NULL || (node->uaddr & mask) !=
> +                                       ((prev_node->uaddr + prev_node->size - 1) & mask)) {
>                                 next_node = RTE_TAILQ_NEXT(node, next);
>                                 /* Don't disable coredump if the next node is in the same page */
>                                 if (next_node == NULL || ((node->uaddr + node->size - 1) & mask) !=
> @@ -283,8 +283,8 @@ vhost_user_iotlb_cache_remove(struct virtio_net *dev, struct vhost_virtqueue *vq
>                         mask = ~(alignment-1);
>
>                         /* Don't disable coredump if the previous node is in the same page */
> -                       if (prev_node == NULL ||
> -                                       (node->uaddr & mask) != (prev_node->uaddr & mask)) {
> +                       if (prev_node == NULL || (node->uaddr & mask) !=
> +                                       ((prev_node->uaddr + prev_node->size - 1) & mask)) {
>                                 next_node = RTE_TAILQ_NEXT(node, next);
>                                 /* Don't disable coredump if the next node is in the same page */
>                                 if (next_node == NULL || ((node->uaddr + node->size - 1) & mask) !=
> --
> 2.39.2
>