Re: Predictable and consistent net interface naming in guests
On Mon, 31 Oct 2022 16:59:53 +0200
Edward Haas <edwardh(a)redhat.com> wrote:
Thank you both for the quick response.
On Mon, Oct 31, 2022 at 4:49 PM Daniel P. Berrangé <berrange(a)redhat.com>
wrote:
> On Mon, Oct 31, 2022 at 04:32:27PM +0200, Edward Haas wrote:
> > Hi Igor and Laine,
> >
> > I would like to revive a 2 years old discussion [1] about consistent
> network
> > interfaces in the guest.
> >
> > That discussion mentioned that a guest PCI address may change in two
> cases:
> > - The PCI topology changes.
> > - The machine type changes.
> >
> > Usually, the machine type is not expected to change, especially if one
> > wants to allow migrations between nodes.
> > I would hope to argue this should not be problematic in practice, because
> > guest images would be made per a specific machine type.
> >
> > Regarding the PCI topology, I am not sure I understand what changes
> > need to occur to the domxml for a defined guest PCI address to change.
> > The only think that I can think of is a scenario where hotplug/unplug is
> > used,
> > but even then I would expect existing devices to preserve their PCI
> address
> > and the plug/unplug device to have a reserved address managed by the one
> > acting on it (the management system).
> >
> > Could you please help clarify in which scenarios the PCI topology can
> cause
> > a mess to the naming of interfaces in the guest?
> >
> > Are there any plans to add the acpi_index support?
>
> This was implemented a year & a half ago
>
> https://libvirt.org/formatdomain.html#network-interfaces
>
> though due to QEMU limitations this only works for the old
> i440fx chipset, not Q35 yet.
>
I think most deployments today use Q35.
Are there plans to resolve it there?
I'm working on it actively. It won't make in this QEMU release but
tentatively it might make into the next one if no complications would
arise.
I'm trying to make it work not only for root-ports/bridges on Q35 but also
for non-hotpluggable NICs attached to root bus (aka integrated endpoints),
so it would be on par with i440fx machines.
BTW, should this limitation be added to the documentation?
limitation (applies both to i440fx and Q35 is that NIC should be
attached to hotpluggable bus where hotplug is managed by ACPI PCI
hotplug handlers)
>
> With regards,
> Daniel
> --
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>