Created attachment 1771545 [details]
the xml of the vm

Description of problem:
guest crash when hotplug an interface

Version-Release number of selected component (if applicable):
➜  ~ rpm -q libvirt qemu-kvm
libvirt-7.3.0-1.fc34.x86_64
qemu-kvm-6.0.0-0.1.rc2.fc35.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Start a vm, then try to hotplug an interface, the vm crashed:
➜  ~ virsh list 
 Id   Name   State
----------------------
 12   pc     running

➜  ~ virsh attach-interface pc network default 
error: Failed to attach interface
error: Unable to read from monitor: Connection reset by peer

➜  ~ virsh list --all
 Id   Name   State
-----------------------
 -    pc     shut off

2. coredump info:
(gdb) c
Continuing.
[Thread 0x7f6287fff640 (LWP 127987) exited]
[New Thread 0x7f6287fff640 (LWP 128024)]
[New Thread 0x7f623d1d3640 (LWP 128025)]
[New Thread 0x7f623c9d2640 (LWP 128026)]

Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
0x000055cabfc04589 in tap_send (opaque=0x55cac227f000) at ../net/tap.c:206
206	        if (!s->nc.peer->do_not_pad) {
(gdb) c
Continuing.
[Thread 0x7f623c9d2640 (LWP 128026) exited]
[Thread 0x7f623d1d3640 (LWP 128025) exited]
[Thread 0x7f6287fff640 (LWP 128024) exited]
[Thread 0x7f62861ff640 (LWP 127995) exited]
[Thread 0x7f62877fe640 (LWP 127992) exited]
[Thread 0x7f628d849640 (LWP 127982) exited]
[Thread 0x7f628d84cec0 (LWP 127977) exited]

Program terminated with signal SIGSEGV, Segmentation fault.
The program no longer exists.
(gdb) 
Actual results:
the vm shutdown when hotplug an interface

Expected results:
the vm should not shutdown and the hotplug should succeed

Additional info: