From: David Woodhouse <dwmw@amazon.co.uk>

When the Xen guest asks to unplug *emulated* NICs, it's kind of unhelpful
also to unplug the peer of the *Xen* PV NIC.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 hw/i386/xen/xen_platform.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/hw/i386/xen/xen_platform.c b/hw/i386/xen/xen_platform.c
index 17457ff3de..e2dd1b536a 100644
--- a/hw/i386/xen/xen_platform.c
+++ b/hw/i386/xen/xen_platform.c
@@ -140,9 +140,14 @@ static void unplug_nic(PCIBus *b, PCIDevice *d, void *o)
 /* Remove the peer of the NIC device. Normally, this would be a tap device. */
 static void del_nic_peer(NICState *nic, void *opaque)
 {
-    NetClientState *nc;
+    NetClientState *nc = qemu_get_queue(nic);
+    ObjectClass *klass = module_object_class_by_name(nc->model);
+
+    /* Only delete peers of PCI NICs that we're about to delete */
+    if (!klass || !object_class_dynamic_cast(klass, TYPE_PCI_DEVICE)) {
+        return;
+    }
 
-    nc = qemu_get_queue(nic);
     if (nc->peer)
         qemu_del_net_client(nc->peer);
 }
-- 
2.40.1

On 17/10/2023 19:25, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> When the Xen guest asks to unplug *emulated* NICs, it's kind of unhelpful
> also to unplug the peer of the *Xen* PV NIC.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>   hw/i386/xen/xen_platform.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/xen/xen_platform.c b/hw/i386/xen/xen_platform.c
> index 17457ff3de..e2dd1b536a 100644
> --- a/hw/i386/xen/xen_platform.c
> +++ b/hw/i386/xen/xen_platform.c
> @@ -140,9 +140,14 @@ static void unplug_nic(PCIBus *b, PCIDevice *d, void *o)
>   /* Remove the peer of the NIC device. Normally, this would be a tap device. */
>   static void del_nic_peer(NICState *nic, void *opaque)
>   {
> -    NetClientState *nc;
> +    NetClientState *nc = qemu_get_queue(nic);
> +    ObjectClass *klass = module_object_class_by_name(nc->model);
> +
> +    /* Only delete peers of PCI NICs that we're about to delete */
> +    if (!klass || !object_class_dynamic_cast(klass, TYPE_PCI_DEVICE)) {

Would it not be better to test for object_class_dynamic_cast(klass, 
TYPE_XEN_DEVICE)?

   Paul

> +        return;
> +    }
>   
> -    nc = qemu_get_queue(nic);
>       if (nc->peer)
>           qemu_del_net_client(nc->peer);
>   }

On Tue, 2023-10-24 at 15:32 +0100, Paul Durrant wrote:
> On 17/10/2023 19:25, David Woodhouse wrote:
> > From: David Woodhouse <dwmw@amazon.co.uk>
> > 
> > When the Xen guest asks to unplug *emulated* NICs, it's kind of unhelpful
> > also to unplug the peer of the *Xen* PV NIC.
> > 
> > Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> > ---
> >    hw/i386/xen/xen_platform.c | 9 +++++++--
> >    1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/i386/xen/xen_platform.c b/hw/i386/xen/xen_platform.c
> > index 17457ff3de..e2dd1b536a 100644
> > --- a/hw/i386/xen/xen_platform.c
> > +++ b/hw/i386/xen/xen_platform.c
> > @@ -140,9 +140,14 @@ static void unplug_nic(PCIBus *b, PCIDevice *d, void *o)
> >    /* Remove the peer of the NIC device. Normally, this would be a tap device. */
> >    static void del_nic_peer(NICState *nic, void *opaque)
> >    {
> > -    NetClientState *nc;
> > +    NetClientState *nc = qemu_get_queue(nic);
> > +    ObjectClass *klass = module_object_class_by_name(nc->model);
> > +
> > +    /* Only delete peers of PCI NICs that we're about to delete */
> > +    if (!klass || !object_class_dynamic_cast(klass, TYPE_PCI_DEVICE)) {
> 
> Would it not be better to test for object_class_dynamic_cast(klass, 
> TYPE_XEN_DEVICE)?

Only if we also change the actual unplug to destroy non-PCI devices too.

The only non-PCI device you could have here is an ISA NE2000, I think.