Qemu falls back on userland handlers even if vhost-user and vhost-vdpa
cases. These assumes a tap device can handle the packets.

If a vdpa device fail to start, it can trigger a sigsegv because of
that. Add dummy receiver that returns no progress so it can keep
running.

Fixes: 1e0a84ea49 ("vhost-vdpa: introduce vhost-vdpa net client")
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 net/vhost-vdpa.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 2e3c22a8c7..25dd6dd975 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -170,9 +170,17 @@ static bool vhost_vdpa_check_peer_type(NetClientState *nc, ObjectClass *oc,
     return true;
 }
 
+/** Dummy receive in case qemu falls back to userland tap networking */
+static ssize_t vhost_vdpa_receive(NetClientState *nc, const uint8_t *buf,
+                                  size_t size)
+{
+    return 0;
+}
+
 static NetClientInfo net_vhost_vdpa_info = {
         .type = NET_CLIENT_DRIVER_VHOST_VDPA,
         .size = sizeof(VhostVDPAState),
+        .receive = vhost_vdpa_receive,
         .cleanup = vhost_vdpa_cleanup,
         .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
         .has_ufo = vhost_vdpa_has_ufo,
-- 
2.27.0

On Thu, Nov 25, 2021 at 6:16 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> Qemu falls back on userland handlers even if vhost-user and vhost-vdpa
> cases. These assumes a tap device can handle the packets.
>
> If a vdpa device fail to start, it can trigger a sigsegv because of
> that. Add dummy receiver that returns no progress so it can keep
> running.
>
> Fixes: 1e0a84ea49 ("vhost-vdpa: introduce vhost-vdpa net client")
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>

Acked-by: Jason Wang <jasowang@redhat.com>

> ---
>  net/vhost-vdpa.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 2e3c22a8c7..25dd6dd975 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -170,9 +170,17 @@ static bool vhost_vdpa_check_peer_type(NetClientState *nc, ObjectClass *oc,
>      return true;
>  }
>
> +/** Dummy receive in case qemu falls back to userland tap networking */
> +static ssize_t vhost_vdpa_receive(NetClientState *nc, const uint8_t *buf,
> +                                  size_t size)
> +{
> +    return 0;
> +}
> +
>  static NetClientInfo net_vhost_vdpa_info = {
>          .type = NET_CLIENT_DRIVER_VHOST_VDPA,
>          .size = sizeof(VhostVDPAState),
> +        .receive = vhost_vdpa_receive,
>          .cleanup = vhost_vdpa_cleanup,
>          .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
>          .has_ufo = vhost_vdpa_has_ufo,
> --
> 2.27.0
>