On Mon, Sep 21, 2026 at 10:12:34AM -0500, Konstantin Shkolnyy wrote:
> On 260917 12:35, Daniel P. Berrangé wrote:
> > On Thu, Sep 17, 2026 at 10:25:32AM -0700, Farhan Ali wrote:
> > >
> > > On 9/11/2026 8:21 AM, Konstantin Shkolnyy wrote:
> > > > @@ -1303,11 +1380,22 @@ static void s390_pcihost_unplug(HotplugHandler
> > > > *hotplug_dev, DeviceState *dev,
> > > > pbdev = S390_PCI_DEVICE(dev);
> > > > pbdev->fid = 0;
> > > > QTAILQ_REMOVE(&s->zpci_devs, pbdev, link);
> > > > - g_hash_table_remove(s->zpci_table, &pbdev->idx);
> > > > + /*
> > > > + * If this QEMU is running a migrated guest, and was
> > > > configured with
> > > > + * more zpci devices than the source QEMU, extra zpci devices
> > > > could be
> > > > + * excluded from zpci_table and invisible to the guest and have
> > > > + * pbdev->idx values duplicating those of active devices. If
> > > > the
> > > > + * pbdev being unplugged is such, the zpci_table entry for
> > > > pbdev->idx
> > > > + * can find a different pbdev which we must not remove.
> > > > + */
> > > > + if (g_hash_table_lookup(s->zpci_table, &pbdev->idx) == pbdev) {
> > > > + g_hash_table_remove(s->zpci_table, &pbdev->idx);
> > > > + }
> > >
> > > If we are migrating, won't we re-create the exact same state and devices
> > > on
> > > the target host? Is it possible that the target QEMU can have more devices
> > > than source?
> >
> > It is expected that the source and dest QEMU processes have identical
> > virtual hardware configuration, and also no attempts should be made to
> > hot-add/remove devices while migration is running.
>
> Do you suggest to completely delete this hunk, or keep as "defensive tactic"
> and correct the comment?
I don't think it is worth trying to add defensive checks, as if the
config is not identical, the code may well not even be reached as
vmstate parsing/loading typically fails during migration.
With regards,
Daniel
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