Currently QEMU always crashes in following scenario (assume that vhost-user application is Open vSwitch with 'dpdkvhostuser' port):
1. # Check that link in guest is in a normal state. [guest]# ip link show eth0 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc <...> link/ether 00:16:35:af:aa:4b brd ff:ff:ff:ff:ff:ff 2. # Kill vhost-user application (using SIGSEGV just to be sure). [host]# kill -11 `pgrep ovs-vswitchd` 3. # Check that guest still thinks that all is good. [guest]# ip link show eth0 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc <...> link/ether 00:16:35:af:aa:4b brd ff:ff:ff:ff:ff:ff 4. # Try to unbind virtio-pci driver and observe QEMU crash. [guest]# echo -n '0000:00:01.0' > /sys/bus/pci/drivers/virtio-pci/unbind qemu: Failed to read msg header. Read 0 instead of 12. Original request 11. qemu: Failed to read msg header. Read 0 instead of 12. Original request 11. qemu: Failed to read msg header. Read 0 instead of 12. Original request 11. Child terminated with signal = 0xb (SIGSEGV) GDBserver exiting After the applying of this patch-set: 4. # Try to unbind virtio-pci driver. Unbind works fine with only few errors. [guest]# echo -n '0000:00:01.0' > /sys/bus/pci/drivers/virtio-pci/unbind qemu: Failed to read msg header. Read 0 instead of 12. Original request 11. qemu: Failed to read msg header. Read 0 instead of 12. Original request 11. 5. # Bind virtio-pci driver back. [guest]# echo -n '0000:00:01.0' > /sys/bus/pci/drivers/virtio-pci/bind 6. # Check link in guest. No crashes here, link in DOWN state. [guest]# ip link show eth0 7: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc <...> link/ether 00:16:35:af:aa:4b brd ff:ff:ff:ff:ff:ff 7. QEMU may be gracefully restarted to restore communication after restarting of vhost-user application. Ilya Maximets (4): vhost-user: fix crash on socket disconnect. vhost: prevent double stop of vhost_net device. vhost: check for vhost_net device validity. net: notify about link status only if it changed. hw/net/vhost_net.c | 48 ++++++++++++++++++++++++++++++++++++++---- hw/net/virtio-net.c | 33 ++++++++++++++++++++++------- include/hw/virtio/virtio-net.h | 1 + include/net/vhost-user.h | 1 + include/net/vhost_net.h | 1 + net/filter.c | 1 + net/net.c | 7 +++--- net/vhost-user.c | 43 +++++++++++++++++++++++++++++-------- 8 files changed, 111 insertions(+), 24 deletions(-) -- 2.5.0