If I manually delete the Q35 USB Controllers, I can use managedsave/start, but I start getting tty errors that don't happen before the managedsave/start. Using libvirt 1.2.18 (-1 Arch) and QEMU git-master (2.4.0.r40384.2d69736). Installed using Q35 chipset. I'm running QEMU git, which allows SCSI controller migration, so I can attempt doing this. I started my guest, and waited for 15 minutes. No post-booting tty1/dmesg messages. After a managedsave/start, I start getting tty1/dmesg errors. I can also no longer ping the guest system. ===== $ dmesg|grep "IRQ 21" [ 1.141040] ACPI: PCI Interrupt Link [GSIF] enabled at IRQ 21 $ ls -lA /proc/irq/21 total 0 -r--r--r-- 1 root root 0 Aug 10 19:42 affinity_hint -r--r--r-- 1 root root 0 Aug 10 19:42 node dr-xr-xr-x 2 root root 0 Aug 10 19:42 qxl -rw-r--r-- 1 root root 0 Aug 10 19:42 smp_affinity -rw-r--r-- 1 root root 0 Aug 10 19:42 smp_affinity_list -r--r--r-- 1 root root 0 Aug 10 19:42 spurious dr-xr-xr-x 2 root root 0 Aug 10 19:42 virtio2 $ ls -lA /proc/irq/21/qxl total 0 $ ls -lA /proc/irq/21/virtio2 total 0 ===== {{{ on host, everything else is on guest }}} virsh # managedsave <vmname> Domain servo state saved by libvirt virsh # start <vmname> Domain <vmname> started ===== [ 1117.083236] irq 21: nobody cared (try booting with the "irqpoll" option) [ 1117.083236] handlers: [ 1117.083236] [<ffffffffa00cfc60>] qxl_irq_handler [qxl] [ 1117.083236] [<ffffffffa00f2530>] vp_interrupt [virtio_pci] [ 1117.083236] Disabling IRQ #21 ===== {{{ bit later, doing nothing, just waiting }}} [ 1440.223239] INFO: task vballoon:147 blocked for more than 120 seconds. [ 1440.223409] Not tainted 4.1.4-1-ARCH #1 [ 1440.223556] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1440.223805] INFO: task btrfs-transacti:242 blocked for more than 120 seconds. [ 1440.223947] Not tainted 4.1.4-1-ARCH #1 [ 1440.224069] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1440.224422] INFO: task systemd-journal:280 blocked for more than 120 seconds. [ 1440.224575] Not tainted 4.1.4-1-ARCH #1 [ 1440.224710] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. {{{ these message lines show up very slowly, as if the VM console video is running at 1% speed }}} ===== {{{ bit later, doing nothing, just waiting }}} [ 1560.223227] {{{ repeats the above 9 lines, vballoon:147/btrfs-transacti:242/systemd-journal:280] blocked for more than 120 seconds }}} ===== {{{ bit later, doing nothing, just waiting }}} [ 1680.223217] {{{ repeats the above 9 lines, vballoon:147/btrfs-transacti:242/systemd-journal:280] blocked for more than 120 seconds }}} [ 1688.885605] systemd[1]: systemd-journald.service: Watchdog timeout (limit 1min)! =====