Re: vepa-mode directly attached interface
Il 2022-06-11 19:32 Laine Stump ha scritto:
libvirt's defaults are defaults, and can't be changed with
config.
libvirt also will never changed the hardcoded default, because that
could break existing installations.
Thanks for the direct confirmation that default can not be changed with
config. I opened a cockpit-machine bug to ask for a change there:
https://bugzilla.redhat.com/show_bug.cgi?id=2095967
I'm not sure why vepa was chosen as the default when macvtap
support
was added to libvirt, but my best guess is that it was just the bias
of the person doing the work who assumed their usage would be the most
common (IIRC it was done by someone who was specifically wanting to
support connection to VEPA-capable switches, and since it was a new
feature nobody else had experience with / opinions about which mode
would be most common, so the reviewers just accepted this default)
Sound reasonable. Do you know if directly attached bridge-mode interface
is common and tested into production workload, or if "pure" bridge mode
is the way to go?
Full disclosure: I always used "pure" bridges, but I like the idea to
deny any guest->host traffic by design - hence my interest in
bridge-mode macvtap interfaces. Moreover, by the virtue of not requiring
a dedicated bridge interface, they can simplify the host network
configuration.
I guess you'll need to do a "virsh dumpxml --inactive"
for each guest
and parse it out of there.
It matches my results. However, virsh dumpxml is an expensive operation
- polkitd can easily burn >30% of a single core for 1s polling interval
with virsh dumpxml. I settled (for testing) with grepping "mode..vepa"
in /etc/libvirtd/qemu and it seems to work well (1s polling not even
register in top).
Does libvirt support calling some external script when a new virtual
machine is defined?
No, I think the mode of the macvtap interface is set when the
interface is created, and can't be changed later (i.e. it's a
limitation of macvtap, not libvirt)
Again, it matches my results (ip link showing "operation not supported"
when trying to change the mode at runtime). I hoped to miss something,
but it does not seem the case...
Thanks.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti(a)assyoma.it - info(a)assyoma.it
GPG public key ID: FF5F32A8