On Wed, Aug 20, 2025 at 8:47 AM David Woodhouse <dw...@infradead.org> wrote:
>
> On Wed, 2025-08-20 at 10:34 +0800, Jason Wang wrote:
> > On Wed, Aug 20, 2025 at 12:13 AM David Woodhouse <dw...@infradead.org>
> > wrote:
> > >
> > > On Mon, 2025-03-10 at 20:22 +0800, Jason Wang wrote:
> > > > From: Eugenio Pérez <epere...@redhat.com>
> > > >
> > > > Commit a0d7215e33 ("vhost-vdpa: do not cleanup the vdpa/vhost-net
> > > > structures if peer nic is present") effectively delayed the backend
> > > > cleanup, allowing the frontend or the guest to access it resources as
> > > > long as the frontend is still visible to the guest.
> > > >
> > > > However it does not clean up the resources until the qemu process is
> > > > over. This causes an effective leak if the device is deleted with
> > > > device_del, as there is no way to close the vdpa device. This makes
> > > > impossible to re-add that device to this or other QEMU instances until
> > > > the first instance of QEMU is finished.
> > > >
> > > > Move the cleanup from qemu_cleanup to the NIC deletion and to
> > > > net_cleanup.
> > > >
> > > > Fixes: a0d7215e33 ("vhost-vdpa: do not cleanup the vdpa/vhost-net
> > > > structures if peer nic is present")
> > > > Reported-by: Lei Yang <leiy...@redhat.com>
> > > > Signed-off-by: Eugenio Pérez <epere...@redhat.com>
> > > > Signed-off-by: Jonah Palmer <jonah.pal...@oracle.com>
> > > > Signed-off-by: Jason Wang <jasow...@redhat.com>
> > >
> > > This crashes QEMU when I launch an emulated Xen guest with a Xen PV
> > > NIC, and quit (using Ctrl-A x on the monitor).
> >
> > Eugenio and Jonah, any thoughts on this? It looks like the code
> > doesn't deal with hub correctly.
>
> The interesting part about Xen netback is that it does its own teardown
> from xen_device_unrealize() because in the case of running under true
> Xen, it needs to clean up XenStore nodes which are externally visible.
> It doesn't all just go away when QEMU exits.
>
> We fixed a potentially similar issue in commit 84f85eb95f14a ("net: do
> not delete nics in net_cleanup()")?
>
I was not aware of that code to be honest :(.
Jonah, could you take a look at this? It should be a matter of
replicating what the series does in the list on NICs, in this linked
list.
Thanks!
