Solarflare
Server
Adapter
User
Guide
SR
‐
IOV
Virtualization
Using
KVM
Issue
20
©
Solarflare
Communications
2017
337
KVM
Direct
Bridged
In
this
configuration
multiple
macvtap
interfaces
are
bound
over
the
same
PF.
For
each
VM
created,
libvirt
will
automatically
instantiate
a
macvtap
driver
instance
and
the
macvtap
interfaces
will
be
visible
on
the
host.
Where
the
KVM
libvirt
bridged
configuration
uses
the
standard
Linux
bridge,
a
direct
bridged
configuration
bypasses
this
providing
an
internal
bridging
function
and
increasing
performance.
When
using
macvtap
there
is
no
link
state
propagation
to
the
guest
which
is
unable
to
identify
if
a
physical
link
is
up
or
down.
Macvtap
does
not
currently
forward
multicast
joins
from
the
guests
to
the
underlying
network
driver
with
the
result
that
all
multicast
traffic
received
by
the
physical
port
is
forwarded
to
all
guests.
Due
to
this
limitation
this
configuration
is
not
recommended
for
deployments
that
use
a
non
‐
trivial
amount
of
multicast
traffic.
Guest
migration
is
fully
supported
as
there
is
no
physical
hardware
state
in
the
VM
guests.
A
guest
can
be
migrated
to
a
host
using
a
different
VF
or
a
host
without
an
SR
‐
IOV
capable
adapter.
Figure
52:
KVM
‐
direct
bridged