[PATCH 0/3] vdpa: Fix SIGSEGV on failed vdpa devices

[PATCH 0/3] vdpa: Fix SIGSEGV on failed vdpa devices

[Eugenio Pérez]

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 receivers that return no progress so it can keep
running.

Tested with a modified version of vp_vdpa to fail negotiation.

This is another bersion of the patch proposed in [1], but the subject
didn't match the patch anymore.

[1] https://lists.nongnu.org/archive/html/qemu-devel/2021-11/msg03719.html

Eugenio Pérez (3):
  virtio-net: Fix indentation
  vdpa: Add dummy receive callbacks
  virtio-net: Fix log message

 hw/net/virtio-net.c | 13 +++++++------
 net/vhost-vdpa.c    | 16 ++++++++++++++++
 2 files changed, 23 insertions(+), 6 deletions(-)

-- 
2.27.0

[PATCH 1/3] virtio-net: Fix indentation

[Eugenio Pérez]

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/net/virtio-net.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index f2014d5ea0..004acf858f 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -3501,7 +3501,7 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
     nc = qemu_get_queue(n->nic);
     nc->rxfilter_notify_enabled = 1;
 
-   if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
+    if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
         struct virtio_net_config netcfg = {};
         memcpy(&netcfg.mac, &n->nic_conf.macaddr, ETH_ALEN);
         vhost_net_set_config(get_vhost_net(nc->peer),
-- 
2.27.0

[PATCH 2/3] vdpa: Add dummy receive callbacks

[Eugenio Pérez]

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 receivers that return 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 | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 2e3c22a8c7..4c75b78304 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -170,9 +170,25 @@ 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_iov(NetClientState *nc,
+                                      const struct iovec *iov, int iovcnt)
+{
+    return 0;
+}
+
+/** Dummy receive in case qemu falls back to userland tap networking */
+static ssize_t vhost_vdpa_receive_raw(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_iov = vhost_vdpa_receive_iov,
+        .receive_raw = vhost_vdpa_receive_raw,
         .cleanup = vhost_vdpa_cleanup,
         .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
         .has_ufo = vhost_vdpa_has_ufo,
-- 
2.27.0

[PATCH 3/3] virtio-net: Fix log message

[Eugenio Pérez]

The message has never been true in the case of non tap networking, so
only tell that userland networking will be used if possible.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/net/virtio-net.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 004acf858f..442082dd8c 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -245,6 +245,7 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
     NetClientState *nc = qemu_get_queue(n->nic);
     int queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
     int cvq = n->max_ncs - n->max_queue_pairs;
+    bool tap_backend = nc->peer->info->type == NET_CLIENT_DRIVER_TAP;
 
     if (!get_vhost_net(nc->peer)) {
         return;
@@ -258,9 +259,9 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
         int r, i;
 
         if (n->needs_vnet_hdr_swap) {
-            error_report("backend does not support %s vnet headers; "
-                         "falling back on userspace virtio",
-                         virtio_is_big_endian(vdev) ? "BE" : "LE");
+            error_report("backend does not support %s vnet headers%s",
+                    virtio_is_big_endian(vdev) ? "BE" : "LE",
+                    tap_backend ? "; falling back on userspace virtio" : "");
             return;
         }
 
@@ -288,8 +289,8 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
         n->vhost_started = 1;
         r = vhost_net_start(vdev, n->nic->ncs, queue_pairs, cvq);
         if (r < 0) {
-            error_report("unable to start vhost net: %d: "
-                         "falling back on userspace virtio", -r);
+            error_report("unable to start vhost net: %d%s", -r,
+                       tap_backend ? " falling back on userspace virtio" : "");
             n->vhost_started = 0;
         }
     } else {
-- 
2.27.0

Re: [PATCH 2/3] vdpa: Add dummy receive callbacks

[Jason Wang]

On Fri, Nov 19, 2021 at 6:20 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 receivers that return 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 | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 2e3c22a8c7..4c75b78304 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -170,9 +170,25 @@ 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_iov(NetClientState *nc,
> +                                      const struct iovec *iov, int iovcnt)
> +{
> +    return 0;
> +}
> +
> +/** Dummy receive in case qemu falls back to userland tap networking */
> +static ssize_t vhost_vdpa_receive_raw(NetClientState *nc, const uint8_t *buf,
> +                                      size_t size)
> +{
> +    return 0;
> +}

It looks to me the .receive_raw is not need, in nc_sendv_compat() we had:

=>  if (flags & QEMU_NET_PACKET_FLAG_RAW && nc->info->receive_raw) {
        ret = nc->info->receive_raw(nc, buffer, offset);
    } else {
        ret = nc->info->receive(nc, buffer, offset);
    }

Thanks

> +
>  static NetClientInfo net_vhost_vdpa_info = {
>          .type = NET_CLIENT_DRIVER_VHOST_VDPA,
>          .size = sizeof(VhostVDPAState),
> +        .receive_iov = vhost_vdpa_receive_iov,
> +        .receive_raw = vhost_vdpa_receive_raw,
>          .cleanup = vhost_vdpa_cleanup,
>          .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
>          .has_ufo = vhost_vdpa_has_ufo,
> --
> 2.27.0
>

Re: [PATCH 0/3] vdpa: Fix SIGSEGV on failed vdpa devices

[Jason Wang]

On Fri, Nov 19, 2021 at 6:20 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 receivers that return no progress so it can keep
> running.
>
> Tested with a modified version of vp_vdpa to fail negotiation.
>
> This is another bersion of the patch proposed in [1], but the subject
> didn't match the patch anymore.
>
> [1] https://lists.nongnu.org/archive/html/qemu-devel/2021-11/msg03719.html
>

As discussed, we need to consider fixing the gRARP transmission issue
on top, any idea on that?

Thanks

> Eugenio Pérez (3):
>   virtio-net: Fix indentation
>   vdpa: Add dummy receive callbacks
>   virtio-net: Fix log message
>
>  hw/net/virtio-net.c | 13 +++++++------
>  net/vhost-vdpa.c    | 16 ++++++++++++++++
>  2 files changed, 23 insertions(+), 6 deletions(-)
>
> --
> 2.27.0
>
>

Re: [PATCH 2/3] vdpa: Add dummy receive callbacks

[Eugenio Perez Martin]

On Mon, Nov 22, 2021 at 4:55 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Fri, Nov 19, 2021 at 6:20 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 receivers that return 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 | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> >
> > diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> > index 2e3c22a8c7..4c75b78304 100644
> > --- a/net/vhost-vdpa.c
> > +++ b/net/vhost-vdpa.c
> > @@ -170,9 +170,25 @@ 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_iov(NetClientState *nc,
> > +                                      const struct iovec *iov, int iovcnt)
> > +{
> > +    return 0;
> > +}
> > +
> > +/** Dummy receive in case qemu falls back to userland tap networking */
> > +static ssize_t vhost_vdpa_receive_raw(NetClientState *nc, const uint8_t *buf,
> > +                                      size_t size)
> > +{
> > +    return 0;
> > +}
>
> It looks to me the .receive_raw is not need, in nc_sendv_compat() we had:
>
> =>  if (flags & QEMU_NET_PACKET_FLAG_RAW && nc->info->receive_raw) {
>         ret = nc->info->receive_raw(nc, buffer, offset);
>     } else {
>         ret = nc->info->receive(nc, buffer, offset);
>     }
>

Right, I will delete the _raw part.

Thanks!

> Thanks
>
> > +
> >  static NetClientInfo net_vhost_vdpa_info = {
> >          .type = NET_CLIENT_DRIVER_VHOST_VDPA,
> >          .size = sizeof(VhostVDPAState),
> > +        .receive_iov = vhost_vdpa_receive_iov,
> > +        .receive_raw = vhost_vdpa_receive_raw,
> >          .cleanup = vhost_vdpa_cleanup,
> >          .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
> >          .has_ufo = vhost_vdpa_has_ufo,
> > --
> > 2.27.0
> >
>