when migrate vm, reboot in guest os, the guest os sometime hang

qemu version:v2.9.0-rc5 release

1.virsh migrate --live 165cf436-312f-47e7-90f2-f8aa63f34893 --copy-storage-inc qemu+ssh://10.59.163.38/system
2.run reboot in guest os, add reboot in /etc/rc.local
3.guest os hang sometime.

strace output of qemu:

ppoll([{fd=9, events=POLLIN}, {fd=8, events=POLLIN}, {fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=30, events=POLLIN}, {fd=31, events=POLLIN}], 6, {0, 0}, NULL, 8) = 0 (Timeout)
ppoll([{fd=9, events=POLLIN}, {fd=8, events=POLLIN}, {fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=30, events=POLLIN}, {fd=31, events=POLLIN}], 6, {0, 698000000}, NULL, 8) = 0 (Timeout)
poll([{fd=20, events=POLLOUT}], 1, 0)   = 1 ([{fd=20, revents=POLLOUT|POLLHUP}])
ppoll([{fd=9, events=POLLIN}, {fd=8, events=POLLIN}, {fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=30, events=POLLIN}, {fd=31, events=POLLIN}], 6, {0, 999000000}, NULL, 8^C <unfinished ...>

Hi,
  What's the last thing the guest outputs before the hang?
  Does it get back to the bios or does it hang before that?
  Has the migration finished at that point or is it still going?

Dave

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