To confirm the issue described in the original fix, I traced the virtio balloon subsystem (using QEMU simpletracing) while the VM:
1.) Loaded from a QEMUFile virtio_set_status 0.000 pid=6248 vdev=0x55dcc49cf968 val=0x0 balloon_event 31433104.748 pid=6248 opaque=0x55dcc49cf968 addr=0x100000000 virtio_balloon_to_target 341.343 pid=6248 target=0x100000000 num_pages=0x0 virtio_set_status 5017492.910 pid=6248 vdev=0x55dcc49cf968 val=0x7 # Driver negotiation finished; running balloon_stats_cb() -> virtqueue_push() virtqueue_fill 16176215.480 pid=6248 vq=0x55dcc4a4c9b0 elem=0x55dcc49cfa98 len=0x0 idx=0x0 virtqueue_flush 6.821 pid=6248 vq=0x55dcc4a4c9b0 count=0x1 virtqueue_flush_vt 2.050 pid=6248 old=0xc4 new=0xc5 inuse=0x1 virtio_notify 1.380 pid=6248 vdev=0x55dcc49cf968 vq=0x55dcc4a4c9b0 Here stats_vq_offset is 0 and elem->index is invalid, making the guest BSOD. 2.) Booted normally ... virtio_set_status 0.754 pid=1133 vdev=0x55c2aec27888 val=0x0 virtio_set_status 21.646 pid=1133 vdev=0x55c2aec27888 val=0x3 virtio_set_status 297.769 pid=1133 vdev=0x55c2aec27888 val=0x7 virtio_queue_notify 20.924 pid=1133 vdev=0x55c2aec27888 n=0x2 vq=0x55c2ae39cb60 virtqueue_pop 29.931 pid=1133 vq=0x55c2ae39cb60 elem=0x55c2aec279b8 in_num=0x0 out_num=0x1 virtio_balloon_get_config 357.561 pid=1133 num_pages=0x0 acutal=0x0 virtio_balloon_get_config 10.239 pid=1133 num_pages=0x0 acutal=0x0 virtio_balloon_get_config 2.862 pid=1133 num_pages=0x0 acutal=0x0 virtio_balloon_get_config 2.761 pid=1133 num_pages=0x0 acutal=0x0 virtio_balloon_set_config 171.747 pid=1133 acutal=0x0 oldacutal=0x0 virtio_balloon_set_config 135.158 pid=1133 acutal=0x0 oldacutal=0x0 virtio_balloon_set_config 103.806 pid=1133 acutal=0x0 oldacutal=0x0 virtio_balloon_set_config 95.435 pid=1133 acutal=0x0 oldacutal=0x0 # Driver negotiation finished; running balloon_stats_cb() -> virtqueue_push() virtqueue_fill 24115244.041 pid=1133 vq=0x55c2ae39cb60 elem=0x55c2aec279b8 len=0x3c idx=0x0 virtqueue_flush 7.069 pid=1133 vq=0x55c2ae39cb60 count=0x1 virtqueue_lol 1.712 pid=1133 old=0x0 new=0x1 inuse=0x1 virtio_notify 1.120 pid=1133 vdev=0x55c2aec27888 vq=0x55c2ae39cb60 virtio_queue_notify 1907.429 pid=1133 vdev=0x55c2aec27888 n=0x2 vq=0x55c2ae39cb60 virtqueue_pop 9.840 pid=1133 vq=0x55c2ae39cb60 elem=0x55c2aec279b8 in_num=0x0 out_num=0x1 ... Here stats_vq_offset is 0x3c (the size of stats_vq_elem), and the request proceeds without problem. I'm currently working on the SRU -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1706058 Title: Windows VM crashes when restoring from file if balloon stats polling is enabled To manage notifications about this bug go to: https://bugs.launchpad.net/cloud-archive/+bug/1706058/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
