On 16/03/2016 12:56, Cornelia Huck wrote: > On Wed, 16 Mar 2016 12:48:22 +0100 > Paolo Bonzini <pbonz...@redhat.com> wrote: > >> >> >> On 16/03/2016 12:32, Cornelia Huck wrote: >>> On Wed, 16 Mar 2016 12:09:02 +0100 >>> Paolo Bonzini <pbonz...@redhat.com> wrote: >>> >>>> On 16/03/2016 11:49, Christian Borntraeger wrote: >>> >>>>> #3 0x00000000800b713e in virtio_blk_data_plane_start (s=0xba232d80) at >>>>> /home/cborntra/REPOS/qemu/hw/block/dataplane/virtio-blk.c:224 >>>>> #4 0x00000000800b4ea0 in virtio_blk_handle_output (vdev=0xb9eee7e8, >>>>> vq=0xba305270) at /home/cborntra/REPOS/qemu/hw/block/virtio-blk.c:590 >>>>> #5 0x00000000800ef3dc in virtio_queue_notify_vq (vq=0xba305270) at >>>>> /home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1095 >>>>> #6 0x00000000800f1c9c in virtio_queue_host_notifier_read (n=0xba3052c8) >>>>> at /home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1785 >>>>> #7 0x00000000800f1e14 in virtio_queue_set_host_notifier_fd_handler >>>>> (vq=0xba305270, assign=false, set_handler=false) at >>>>> /home/cborntra/REPOS/qemu/hw/virtio/virtio.c:1817 >>>>> #8 0x0000000080109c50 in virtio_ccw_set_guest2host_notifier >>>>> (dev=0xb9eed6a0, n=0, assign=false, set_handler=false) at >>>>> /home/cborntra/REPOS/qemu/hw/s390x/virtio-ccw.c:97 >>>>> #9 0x0000000080109ef2 in virtio_ccw_stop_ioeventfd (dev=0xb9eed6a0) at >>>>> /home/cborntra/REPOS/qemu/hw/s390x/virtio-ccw.c:154 >>>> >>>> One bug is here: virtio_ccw_stop_ioeventfd, in this case, should pass >>>> assign=true to virtio_ccw_set_guest2host_notifier. (Assuming my >>>> understanding of assign=true is correct; I think it means "I'm going to >>>> set up another host notifier handler"). >>> >>> Hm... I copied these semantics from virtio-pci, and they still seem to >>> be the same. I wonder why we never saw this on virtio-pci? >> >> Just because we never ran the right tests, probably. The bug is indeed >> in virtio-pci as well (I didn't check mmio). > > Somebody should probably do a writeup on the expected behaviour, as > this always ends in mental gymnastics (at least for me :)
Yeah, it doesn't help that the functions are underdocumented (as in the "assign" parameter above). >> >>>> In dataplane, instead, all calls to >>>> virtio_queue_set_host_notifier_fd_handler and >>>> virtio_queue_aio_set_host_notifier_handler should have assign=true. The >>>> ioeventfd is just being moved from one aiocontext to another. >>> >>> How can a transport know where they are called from? >> >> That's a bug in dataplane. The calls should be changed in >> hw/block/dataplane/virtio-blk.c > > I don't think the ->set_host_notifiers() api really allows for this. I think it does, assign is the last argument to k->set_host_notifier(). Paolo
