In hotplugging scenario, taking those true branch, the file
handler do not be closed. Let's close them before return.
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
commit 5193e5fb (tap: factor out common tap initialization)
introduce net_init_tap_one(). But it's inappropriate that
we close fd in net_init_tap_one(), we should lay it in the
caller, becuase some callers needn't to close it if we get
the fd by monitor_handle_fd_param().
On the other hand, in other exceptional branches fd isn't
closed, so that's incomplete anyway.
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Use vhost_set_backend_type to initialise a proper vhost_ops structure.
In vhost_net_init and vhost_net_start_one call conditionally TAP related
initialisation depending on the vhost backend type.
Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
vhost_dev_init will replace devfd and devpath with a single opaque argument.
This is initialised with a file descriptor. When TAP is used (through
vhost_net), open /dev/vhost-net and pass the fd as an opaque parameter in
VhostNetOptions. The same applies to vhost-scsi - open /dev/vhost-scsi and
pass the fd.
Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Avoid iterations for fd 0, 1 & 2 when we are closing file fds in child process.
Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The net subsystem has a control flow mechanism so peer NetClientStates
can tell each other to stop sending packets. This is used to stop
monitoring the tap file descriptor for incoming packets if the guest rx
ring has no spare buffers.
There is a corner case when tap_can_send() is true at the beginning of
an event loop iteration but becomes false before the tap_send() fd
handler is invoked.
tap_send() will read the packet from the tap file descriptor and attempt
to send it. The net queue will hold on to the packet and return 0,
indicating that further I/O is not possible. tap then stops monitoring
the file descriptor for reads.
This is unlike the normal case where tap_can_send() is the same before
and during the event loop iteration. The event loop would simply not
monitor the file descriptor if tap_can_send() returns true. Upon next
iteration it would check tap_can_send() again and begin monitoring if we
can send.
The deadlock happens because tap_send() explicitly disabled read_poll.
This is done with the expectation that the peer will call
qemu_net_queue_flush(). But hw/net/virtio-net.c does not monitor
vm_running transitions and issue the flush. Hence we're left with a
broken tap device.
Cc: qemu-stable@nongnu.org
Reported-by: Neil Skrypuch <neil@tembosocial.com>
Tested-by: Neil Skrypuch <neil@tembosocial.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Since TAP offloadings are manipulated through a new API, it's
not necessary to export them in include/net/tap.h anymore.
Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The TAP NetClientInfo structure is inizialized with the TAP-specific
functions that manipulates offloading features.
Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The tap_has_vnet_hdr() and tap_has_vnet_hdr_len() functions used
to return int, even though they only return true/false values.
This patch changes the prototypes to return bool.
Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This patch forbid the following invalid parameters to tap:
1) fd and vhostfds were specified but vhostfd were not specified
2) vhostfds were specified but fds were not specified
3) fds and vhostfd were specified
For 1 and 2, net_init_tap_one() will still pass NULL as vhostfdname to
monitor_handle_fd_param(), which may crash the qemu.
Also remove the unnecessary has_fd check.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <shajnocz@redhat.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Only tap->vhostfd were checked net_init_tap_one(), but tap->vhostfds were
forgot, this will lead qemu to ignore all fds passed by management through
vhostfds, and tries to create vhost_net device itself. Fix by adding this check
also.
Reportyed-by: Michal Privoznik <mprivozn@redhat.com>
Cc: Michal Privoznik <mprivozn@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Many of these should be cleaned up with proper qdev-/QOM-ification.
Right now there are many catch-all headers in include/hw/ARCH depending
on cpu.h, and this makes it necessary to compile these files per-target.
However, fixing this does not belong in these patches.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Socket buffer sizes were hard-coded to 4K for VDE and socket netdevs. Bump this
up to 68K (ala tap netdev) to handle maximum GSO packet size (64k) plus plenty
of room for the ethernet and virtio_net headers.
Originally, ran into this limitation when using -netdev UDP sockets to connect
VM-to-VM, where VM interface is configure with MTU=9000. (Using virtio_net
NIC model). Test is simple: ping -M do -s 8500 <target>. This test will
attempt to ping with unfragmented packet of given size. Without patch, size
is limited to < 4K (minus protocol hdrs). With patch, ping test works with pkt
size up to 9000 (again, minus protocol hdrs).
v2: per Stefan, increase buf size to (4096+65536) as done in tap and apply
to vde and socket netdevs.
v1: increase buf size to 12K just for -netdev UDP sockets
Signed-off-by: Scott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Fix various typos and misspellings. The bulk of these were found with
codespell.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Obviously, hub does not support multiqueue tap. So this patch forbids creating
multiple queue tap when hub is used to prevent the crash when command line such
as "-net tap,queues=2" is used.
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The multiqueue patch series broke -netdev tap,fd=X which manifests
as libvirt not being able to start a guest. This was because it
passed NULL for the netdev name which results in an anonymous netdev
device regardless of what the user specified.
Cc: Jason Wang <jasowang@redhat.com>
Cc: Bruce Rogers <brogers@suse.com>
Reported-by: Bruce Rogers <brogers@suse.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Recently, linux support multiqueue tap which could let userspace call TUNSETIFF
for a signle device many times to create multiple file descriptors as
independent queues. User could also enable/disabe a specific queue through
TUNSETQUEUE.
The patch adds the generic infrastructure to create multiqueue taps. To achieve
this a new parameter "queues" were introduced to specify how many queues were
expected to be created for tap by qemu itself. Alternatively, management could
also pass multiple pre-created tap file descriptors separated with ':' through a
new parameter fds like -netdev tap,id=hn0,fds="X:Y:..:Z". Multiple vhost file
descriptors could also be passed in this way.
Each TAPState were still associated to a tap fd, which mean multiple TAPStates
were created when user needs multiqueue taps. Since each TAPState contains one
NetClientState, with the multiqueue nic support, an N peers of NetClientState
were built up.
A new parameter, mq_required were introduce in tap_open() to create multiqueue
tap fds.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This patch introduce a new bit - enabled in TAPState which tracks whether a
specific queue/fd is enabled. The tap/fd is enabled during initialization and
could be enabled/disabled by tap_enalbe() and tap_disable() which calls platform
specific helpers to do the real work. Polling of a tap fd can only done when
the tap was enabled.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This patch factors out the common initialization of tap into a new helper
net_init_tap_one(). This will be used by multiqueue tap patches.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Move public headers to include/net, and leave private headers in net/.
Put the virtio headers in include/net/tap.h, removing the multiple copies
that existed. Leave include/net/tap.h as the interface for NICs, and
net/tap_int.h as the interface for OS-specific parts of the tap backend.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Touching char/char.h basically causes the whole of QEMU to
be rebuilt. Avoid this, it is usually unnecessary.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
For tap, we currently assume the vnet header size is 10
(the default value) but that might not be the case
if tap is persistent and has been used by qemu previously.
To fix, set host header size in tap device on open.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This patch doesn't seem much useful alone, I must admit. However,
it makes sense as part of the upcoming directory reorganization,
where I want to have include/net/tap.h as the net<->hw interface
for tap. Then having both net/tap.h and include/net/tap.h does
not work. "Fixed" by moving all the init functions to a single
header file net/clients.h.
The patch also adopts a uniform style for including net/*.h files
from net/*.c, without the net/ path.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
This patch renames+moves the net_handle_fd_param() caller used to
obtain a file descriptor from either qemu_parse_fd() (the normal case)
or from monitor_get_fd() (migration case) into a generically prefixed
monitor_handle_fd_param() to be used by vhost-scsi code.
Also update net/[socket,tap].c consumers to use the new prefix.
Reported-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The vlan feature is no longer part of net core. Rename VLANClientState
to NetClientState because net clients are not explicitly associated with
a vlan at all, instead they have a peer net client to which they are
connected.
This patch is a mechanical search-and-replace except for a few
whitespace fixups where changing VLANClientState to NetClientState
misaligned whitespace.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Since hubs are now used to implement the 'vlan' feature and the vlan
argument is always NULL, remove the argument entirely and update all net
clients that use qemu_new_net_client().
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Stop using the special-case vlan code in net.c. Instead use the hub net
client to implement the vlan feature. The next patch will remove vlan
code from net.c completely.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
The net_client_init() prototype is kept intact.
Based on "is_netdev", the QemuOpts-rooted QemuOpt-list is parsed as a
Netdev or a NetLegacy. The original meat of net_client_init() is moved to
and simplified in net_client_init1():
Fields not common between -net and -netdev are clearly separated. Getting
the name for the init functions is cleaner: Netdev::id is mandatory, and
all init functions handle a NULL NetLegacy::name. NetLegacy::vlan
explicitly depends on -net (see below).
Verifying the "type=" option for -netdev can be turned into a switch.
Format validation with qemu_opts_validate() can be removed because the
visitor covers it. Relatedly, the "net_client_types" array is reduced to
an array of init functions that can be directly indexed by opts->kind.
(Help text is available in the schema JSON.)
The outermost negation in the condition around qemu_find_vlan() was
flattened, because it expresses the dependent code's requirements more
clearly.
VLAN lookup is avoided if there's no init function to pass the VLAN to.
Whenever the value of type=... is needed, we substitute
NetClientOptionsKind_lookup[kind].
The individual init functions are not converted yet, thus the original
QemuOpts instance is passed transparently.
v1->v2:
- NetLegacy::name is optional. Tracked it through all init functions: they
all handle a NULL name. Updated commit message accordingly.
v2->v3:
- NetLegacy::id is allowed and takes precedence over NetLegacy::name.
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
This is needed to get file descriptors from SCM_RIGHTS.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
The only backend that really uses it is the socket one, which calls
monitor_get_fd(). But it can use 'cur_mon' instead.
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-By: Laszlo Ersek <lersek@redhat.com>
The most common use of -net tap is to connect a tap device to a bridge. This
requires the use of a script and running qemu as root in order to allocate a
tap device to pass to the script.
This model is great for portability and flexibility but it's incredibly
difficult to eliminate the need to run qemu as root. The only really viable
mechanism is to use tunctl to create a tap device, attach it to a bridge as
root, and then hand that tap device to qemu. The problem with this mechanism
is that it requires administrator intervention whenever a user wants to create
a guest.
By essentially writing a helper that implements the most common qemu-ifup
script that can be safely given cap_net_admin, we can dramatically simplify
things for non-privileged users. We still support existing -net tap options
as a mechanism for advanced users and backwards compatibility.
Currently, this is very Linux centric but there's really no reason why it
couldn't be extended for other Unixes.
A typical invocation would be similar to one of the following:
qemu linux.img -net bridge -net nic,model=virtio
qemu linux.img -net tap,helper="/usr/local/libexec/qemu-bridge-helper"
-net nic,model=virtio
qemu linux.img -netdev bridge,id=hn0
-device virtio-net-pci,netdev=hn0,id=nic1
qemu linux.img -netdev tap,helper="/usr/local/libexec/qemu-bridge-helper",id=hn0
-device virtio-net-pci,netdev=hn0,id=nic1
The default bridge that we attach to is br0. The thinking is that a distro
could preconfigure such an interface to allow out-of-the-box bridged networking.
Alternatively, if a user wants to use a different bridge, a typical invocation
would be simliar to one of the following:
qemu linux.img -net bridge,br=qemubr0 -net nic,model=virtio
qemu linux.img -net tap,helper="/usr/local/libexec/qemu-bridge-helper --br=qemubr0"
-net nic,model=virtio
qemu linux.img -netdev bridge,br=qemubr0,id=hn0
-device virtio-net-pci,netdev=hn0,id=nic1
qemu linux.img -netdev tap,helper="/usr/local/libexec/qemu-bridge-helper --br=qemubr0",id=hn0
-device virtio-net-pci,netdev=hn0,id=nic1
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Richa Marwaha <rmarwah@linux.vnet.ibm.com>
Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This patch fixes a bug where child processes of launch_script() can
misbehave due to SIGCHLD being blocked. In the case of `sudo`, this
causes a permanent hang.
Previously a SIGCHLD handler was added to reap fork_exec()'d zombie
processes by calling waitpid(-1, ...). This required other
fork()/waitpid() callers to temporarilly block SIGCHILD to avoid
having the final wait status being intercepted by the SIGCHLD
handler:
7c3370d4fe
Since then, the qemu_add_child_watch() interface was added to allow
registration of such processes and reap only from that specific set
of PIDs:
4d54ec7898
As a result, we can now avoid blocking SIGCHLD in launch_script(), so
drop that behavior.
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This patch removes all references to signal.h when qemu-common.h is included
as they become redundant.
Signed-off-by: Alexandre Raymond <cerbere@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
When MSI is off, each interrupt needs to be bounced through the io
thread when it's set/cleared, so vhost-net causes more context switches and
higher CPU utilization than userspace virtio which handles networking in
the same thread.
We'll need to fix this by adding level irq support in kvm irqfd,
for now disable vhost-net in these configurations.
Added a vhostforce flag to force vhost-net back on.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
virtio-net expects set_offload to succeed after
peer cleanup.
Since we don't have an open fd anymore, make it so.
Fixes warning about the failure of offload setting.
Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Frontends calling tap_get_vhost_net get an invalid pointer after the
peer backend has been deleted. Jason Wang <jasowang@redhat.com> reports
this leading to a crash in ack_features when we remove the vhost-net
bakend of a virtio nic.
The fix is simply to clear the backend pointer.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Make host vnet header length a structure field in
preparation for using this support in linux kernel.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
will be used by virtio-net for vhost net support
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This adds vhost binary option to tap, to enable vhost net accelerator.
Default is off for now, we'll be able to make default on long term
when we know it's stable.
vhostfd option can be used by management, to pass in the fd. Assigning
vhostfd implies vhost=on.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Will be used by vhost to attach/detach to backend.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Right now, downscript is not invoked reliably. If you execute 'quit' from the
monitor, it won't be invoked.
This fixes that by converting tap to use an exit_notifier to execute the
downscript. In this case, allowing an exit notifier to include state is
critically important for the conversion.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
error_report() terminates the message with a newline. Strip it it
from its arguments.
This fixes a few error messages lacking a newline:
net_handle_fd_param()'s "No file descriptor named %s found", and
tap_open()'s "vnet_hdr=1 requested, but no kernel support for
IFF_VNET_HDR available" (all three versions).
There's one place that passes arguments without newlines
intentionally: load_vmstate(). Fix it up.
net_check_clients() prints this when an VLAN has host devices, but no
guest devices. It uses VLANState members nb_guest_devs and
nb_host_devs to keep track of these devices. However, -device does
not update nb_guest_devs, only net_init_nic() does that, for -net nic.
Check the VLAN clients directly, and remove the counters.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
When vhost is bound to a backend device, we need to stop polling it when
vhost is started, and restart polling when vhost is stopped.
Add an API for that for use by vhost, and implement in tap backend.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
net_tap_init() always sets vnet_hdr using qemu_opt_get_bool(), but
initialize it in net_init_tap() just to reduce confusion.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Add a NetClientInfo pointer to VLANClientState and use that
for the typecode and function pointers.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Okay, let's try re-enabling the drain-entire-queue behaviour, with a
difference - before each subsequent packet, use qemu_can_send_packet()
to check that we can send it. This is similar to how we check before
polling the tap fd and avoids having to drop a packet if the receiver
cannot handle it.
This patch should be a performance improvement since we no longer have
to go through the mainloop for each packet.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
If qemu_send_packet_async() returns zero, it means the packet has been
queued and the sent callback will be invoked once it has been flushed.
This is only possible where the NIC's receive() handler returns zero
and promises to notify the networking core that room is available in its
queue again.
In the case where the receive handler does not have this capability
(and its queue fills up) it returns -1 and the networking core does not
queue up the packet. This condition is indicated by a -1 return from
qemu_send_packet_async().
Currently, tap handles this condition simply by dropping the packet. It
should do its best to avoid getting into this situation by checking such
NIC's have room for a packet before copying the packet from the tap
interface.
tap_send() used to achieve this by only reading a single packet before
returning to the mainloop. That way, tap_can_send() is called before
reading each packet.
tap_send() was changed to completely drain the tap interface queue
without taking into account the situation where the NIC returns an
error and the packet is not queued. Let's start fixing this by
reverting to the previous behaviour of reading one packet at a time.
Reported-by: Scott Tsai <scottt.tw@gmail.com>
Tested-by: Sven Rudolph <Sven_Rudolph@drewag.de>
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Currently compiling the tap sources breaks on Mac OS X. This is because of:
1) tap-linux.h requiring Linux includes
2) typos
3) missing #includes
This patch adds what's necessary to compile tap happily on Mac OS X.
I haven't tested if using tap actually works, but I don't think that's a
major issue as that code was probably seriously untested before already.
I didn't split the patch, because it's only a few lines of code and
splitting is probably not worth the effort here.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Okay, this makes the tap options available on AIX even though there's
no support, but if we want to do it right we should have not compile
the tap code at all on AIX using e.g. CONFIG_TAP.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
