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Re: [Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bi

From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net
Date: Tue, 12 Jun 2018 09:54:44 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0

On 2018年06月12日 01:26, Michael S. Tsirkin wrote:
On Mon, May 07, 2018 at 04:09:54PM -0700, Sridhar Samudrala wrote:
This feature bit can be used by hypervisor to indicate virtio_net device to
act as a standby for another device with the same MAC address.

I tested this with a small change to the patch to mark the STANDBY feature 
by default as i am using libvirt to start the VMs.
Is there a way to pass the newly added feature bit 'standby' to qemu via libvirt
XML file?

Signed-off-by: Sridhar Samudrala <address@hidden>
So I do not think we can commit to this interface: we
really need to control visibility of the primary device.

The problem is legacy guest won't use primary device at all if we do this.

How about control the visibility of standby device?


However just for testing purposes, we could add a non-stable
interface "x-standby" with the understanding that as any
x- prefix it's unstable and will be changed down the road,
likely in the next release.

  hw/net/virtio-net.c                         | 2 ++
  include/standard-headers/linux/virtio_net.h | 3 +++
  2 files changed, 5 insertions(+)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 90502fca7c..38b3140670 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -2198,6 +2198,8 @@ static Property virtio_net_properties[] = {
      DEFINE_PROP_INT32("speed", VirtIONet, net_conf.speed, SPEED_UNKNOWN),
      DEFINE_PROP_STRING("duplex", VirtIONet, net_conf.duplex_str),
+    DEFINE_PROP_BIT64("standby", VirtIONet, host_features, 
+                      false),
diff --git a/include/standard-headers/linux/virtio_net.h b/include/standard-headers/linux/virtio_net.h
index e9f255ea3f..01ec09684c 100644
--- a/include/standard-headers/linux/virtio_net.h
+++ b/include/standard-headers/linux/virtio_net.h
@@ -57,6 +57,9 @@
                                         * Steering */
  #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */
+#define VIRTIO_NET_F_STANDBY 62 /* Act as standby for another device
+                                         * with the same MAC.
+                                         */
  #define VIRTIO_NET_F_SPEED_DUPLEX 63  /* Device set linkspeed and duplex */

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