On Fri, 11 Oct 2019 13:20:06 +0200
Jens Freimann <address@hidden> wrote:
This adds support for hiding a device to the qbus and qdev APIs. The
first user of this will be the virtio-net failover feature but the API
introduced with this patch could be used to implement other features as
well, for example hiding pci devices when a pci bus is powered off.
qdev_device_add() is modified to check for a net_failover_pair_id
argument in the option string. A DeviceListener callback
should_be_hidden() is added. It can be used by a standby device to
inform qdev that this device should not be added now. The standby device
handler can store the device options to plug the device in at a later
point in time.
One reason for hiding the device is that we don't want to expose both
devices to the guest kernel until the respective virtio feature bit
VIRTIO_NET_F_STANDBY was negotiated and we know that the devices will be
handled correctly by the guest.
More information on the kernel feature this is using:
https://www.kernel.org/doc/html/latest/networking/net_failover.html
An example where the primary device is a vfio-pci device and the standby
device is a virtio-net device:
A device is hidden when it has an "net_failover_pair_id" option, e.g.
-device virtio-net-pci,...,failover=on,...
-device vfio-pci,...,net_failover_pair_id=net1,...
Signed-off-by: Jens Freimann <address@hidden>
---
hw/core/qdev.c | 19 +++++++++++++++++++
include/hw/qdev-core.h | 9 +++++++++
qdev-monitor.c | 43 ++++++++++++++++++++++++++++++++++++++----
vl.c | 6 ++++--
4 files changed, 71 insertions(+), 6 deletions(-)
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index cbad6c1d55..84fac591ca 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -212,6 +212,25 @@ void device_listener_unregister(DeviceListener *listener)
QTAILQ_REMOVE(&device_listeners, listener, link);
}
+bool qdev_should_hide_device(QemuOpts *opts, Error **errp)
+{
+ bool res = false;
+ bool match_found = false;
+ DeviceListener *listener;
+
+ QTAILQ_FOREACH(listener, &device_listeners, link) {
+ if (listener->should_be_hidden) {
+ listener->should_be_hidden(listener, opts, &match_found, &res);
+ }
+
+ if (match_found) {
+ break;
+ }
Calling convention here seems overly complicated, couldn't
should_be_hidden() just return >0 (should be hidden), 0 (should not be
hidden), <0 (don't care), ie. continue until >=0? The errp arg is
unused and using "res" to return should/shouldn't hide is very unclear.
The virtio callback renames this to hide, which makes more sense, but
as above, both the stop and hidden state could be conveyed with a
simple int return value. Thanks,