Solarflare
Server
Adapter
User
Guide
SR
‐
IOV
Virtualization
Using
KVM
Issue
20
©
Solarflare
Communications
2017
340
KVM
Libvirt
Direct
Passthrough
Using
a
libvirt
direct
‐
passthrough
configuration,
VFs
are
used
in
the
host
OS
to
provide
network
acceleration
for
guest
VMs.
The
guest
continues
to
use
a
paravirtualized
driver
and
is
unaware
this
is
backed
with
a
VF
from
the
network
adapter.
Figure
54:
SR
‐
IOV
VFs
used
in
the
host
OS
•
The
Solarflare
net
driver
is
bound
over
the
top
of
each
VF.
•
Each
macvtap
interface
is
implicitly
created
by
libvirt
over
a
single
VF
network
interface
and
is
not
visible
to
the
host
OS.
•
Each
macvtap
instance
builds
over
a
different
network
interface
‐
so
there
is
no
implicit
macvtap
bridge.
•
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
reconfigured
to
a
host
using
a
different
VF
or
a
host
without
an
SR
‐
IOV
capable
adapter.
•
The
MAC
address
from
the
VF
is
passed
through
to
the
para
‐
virtualized
driver.