On Fri, 11 Nov 2016 20:46:53 +0000
Felipe Franciosi <fel...@nutanix.com> wrote:
> The trace you showed is exactly the same I encountered on vhost-scsi. And the
> one my (hacky) patched fixed. The summary of my investigation is on the patch
> description. I'm OOO so apologies for not being of more help. F.
Paolo's patch states that it overrides your patch, so I used Paolo's
patch alone, but adding yours doesn't change anything, same assertion.
Thanks,
Alex
> > On 11 Nov 2016, at 20:38, Alex Williamson <alex.william...@redhat.com>
> > wrote:
> >
> > On Fri, 11 Nov 2016 20:28:55 +0100
> > Paolo Bonzini <pbonz...@redhat.com> wrote:
> >
> >> Following the recent refactoring of virtio notifiers [1], more specifically
> >> the patch ed08a2a0b ("virtio: use virtio_bus_set_host_notifier to
> >> start/stop ioeventfd") that uses virtio_bus_set_host_notifier [2]
> >> by default, core virtio code requires 'ioeventfd_started' to be set
> >> to true/false when the host notifiers are configured.
> >>
> >> When vhost is stopped and started, however, there is a stop followed by
> >> another start. Since ioeventfd_started was never set to true, the 'stop'
> >> operation triggered by virtio_bus_set_host_notifier() will not result
> >> in a call to virtio_pci_ioeventfd_assign(assign=false). This leaves
> >> the memory regions with stale notifiers and results on the next start
> >> triggering the following assertion:
> >>
> >> kvm_mem_ioeventfd_add: error adding ioeventfd: File exists
> >> Aborted
> >>
> >> This patch reintroduces (hopefully in a cleaner way) the concept
> >> that was present with ioeventfd_disabled before the refactoring.
> >> When ioeventfd_grabbed>0, ioeventfd_started tracks whether ioeventfd
> >> should be enabled or not, but ioeventfd is actually not started at
> >> all until vhost releases the host notifiers.
> >>
> >> [1] http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg07748.html
> >> [2] http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg07760.html
> >>
> >> Reported-by: Felipe Franciosi <fel...@nutanix.com>
> >> Reported-by: Christian Borntraeger <borntrae...@de.ibm.com>
> >> Reported-by: Alex Williamson <alex.william...@redhat.com>
> >> Fixes: ed08a2a0b ("virtio: use virtio_bus_set_host_notifier to start/stop
> >> ioeventfd")
> >> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> >> ---
> >> You know you really screwed up when you get three Reported-bys...
> >> The patch is largish, but I've added lots of comments.
> >> It overrides Felipe's patch which did not for example fix vhost
> >> multiqueue (tests/vhost-user-test).
> >>
> >> hw/virtio/vhost.c | 11 ++++------
> >> hw/virtio/virtio-bus.c | 50
> >> ++++++++++++++++++++++++++++++++++++------
> >> hw/virtio/virtio.c | 16 ++++++++++++++
> >> include/hw/virtio/virtio-bus.h | 14 ++++++++++++
> >> include/hw/virtio/virtio.h | 2 ++
> >> 5 files changed, 79 insertions(+), 14 deletions(-)
> >
> > I'm not entirely sure what to apply this to, it has conflicts with
> > MST's last pull request, so I applied it to mainline, which for me was:
> >
> > 6bbcb76 MAINTAINERS: Remove obsolete stable branches
> >
> > But this just gives me a different failure, QEMU reports:
> >
> > kvm_mem_ioeventfd_add: error adding ioeventfd: File exists
> >
> > gdb backtrace:
> >
> > Thread 4 "CPU 1/KVM" received signal SIGABRT, Aborted.
> > [Switching to Thread 0x7f60e4ce9700 (LWP 12239)]
> > 0x00007f60f582b765 in __GI_raise (sig=sig@entry=6) at
> > ../sysdeps/unix/sysv/linux/raise.c:54
> > 54 return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);
> > (gdb) bt
> > #0 0x00007f60f582b765 in __GI_raise (sig=sig@entry=6) at
> > ../sysdeps/unix/sysv/linux/raise.c:54
> > #1 0x00007f60f582d36a in __GI_abort () at abort.c:89
> > #2 0x000055af0a40a8f0 in kvm_mem_ioeventfd_add (listener=0x55af0b4d6e70,
> > section=0x7f60e4ce5ef0, match_data=false, data=0, e=0x55af0c2e3690)
> > at /net/gimli/home/alwillia/Work/qemu.git/kvm-all.c:898
> > #3 0x000055af0a4111d6 in address_space_add_del_ioeventfds
> > (as=0x55af0aedef00 <address_space_memory>, fds_new=0x7f60d8000c00,
> > fds_new_nb=9, fds_old=0x7f60d4319e80, fds_old_nb=8)
> > at /net/gimli/home/alwillia/Work/qemu.git/memory.c:757
> > #4 0x000055af0a4114e4 in address_space_update_ioeventfds
> > (as=0x55af0aedef00 <address_space_memory>) at
> > /net/gimli/home/alwillia/Work/qemu.git/memory.c:803
> > #5 0x000055af0a411d1c in memory_region_transaction_commit () at
> > /net/gimli/home/alwillia/Work/qemu.git/memory.c:932
> > #6 0x000055af0a414881 in memory_region_add_eventfd (mr=0x55af0bbcf740,
> > addr=0, size=0, match_data=false, data=0, e=0x55af0c2e3690) at
> > /net/gimli/home/alwillia/Work/qemu.git/memory.c:1984
> > #7 0x000055af0a71b0a8 in virtio_pci_ioeventfd_assign (d=0x55af0bbcea20,
> > notifier=0x55af0c2e3690, n=0, assign=true) at hw/virtio/virtio-pci.c:300
> > #8 0x000055af0a7216f1 in virtio_bus_set_host_notifier (bus=0x55af0bbd6db8,
> > n=0, assign=true) at hw/virtio/virtio-bus.c:257
> > #9 0x000055af0a48180b in vhost_dev_enable_notifiers (hdev=0x55af0b4d4f10,
> > vdev=0x55af0bbd6e30) at
> > /net/gimli/home/alwillia/Work/qemu.git/hw/virtio/vhost.c:1198
> > #10 0x000055af0a457941 in vhost_net_start_one (net=0x55af0b4d4f10,
> > dev=0x55af0bbd6e30) at
> > /net/gimli/home/alwillia/Work/qemu.git/hw/net/vhost_net.c:227
> > #11 0x000055af0a457e2d in vhost_net_start (dev=0x55af0bbd6e30,
> > ncs=0x55af0c7e1890, total_queues=1) at
> > /net/gimli/home/alwillia/Work/qemu.git/hw/net/vhost_net.c:324
> > #12 0x000055af0a4523f2 in virtio_net_vhost_status (n=0x55af0bbd6e30,
> > status=7 '\a') at
> > /net/gimli/home/alwillia/Work/qemu.git/hw/net/virtio-net.c:156
> > #13 0x000055af0a45268e in virtio_net_set_status (vdev=0x55af0bbd6e30,
> > status=7 '\a') at
> > /net/gimli/home/alwillia/Work/qemu.git/hw/net/virtio-net.c:229
> > #14 0x000055af0a478874 in virtio_set_status (vdev=0x55af0bbd6e30, val=7
> > '\a') at /net/gimli/home/alwillia/Work/qemu.git/hw/virtio/virtio.c:898
> > #15 0x000055af0a71b3c0 in virtio_ioport_write (opaque=0x55af0bbcea20,
> > addr=18, val=7) at hw/virtio/virtio-pci.c:383
> > #16 0x000055af0a71b824 in virtio_pci_config_write (opaque=0x55af0bbcea20,
> > addr=18, val=7, size=1) at hw/virtio/virtio-pci.c:508
> > #17 0x000055af0a4102fd in memory_region_write_accessor (mr=0x55af0bbcf310,
> > addr=18, value=0x7f60e4ce64b8, size=1, shift=0, mask=255, attrs=...)
> > at /net/gimli/home/alwillia/Work/qemu.git/memory.c:526
> > #18 0x000055af0a410515 in access_with_adjusted_size (addr=18,
> > value=0x7f60e4ce64b8, size=1, access_size_min=1, access_size_max=4, access=
> > 0x55af0a410213 <memory_region_write_accessor>, mr=0x55af0bbcf310,
> > attrs=...) at /net/gimli/home/alwillia/Work/qemu.git/memory.c:592
> > #19 0x000055af0a412c55 in memory_region_dispatch_write (mr=0x55af0bbcf310,
> > addr=18, data=7, size=1, attrs=...) at
> > /net/gimli/home/alwillia/Work/qemu.git/memory.c:1323
> > #20 0x000055af0a3be583 in address_space_write_continue (as=0x55af0aedede0
> > <address_space_io>, addr=49458, attrs=..., buf=0x7f6110aa0000 "\a", len=1,
> > addr1=18, l=1, mr=0x55af0bbcf310)
> > at /net/gimli/home/alwillia/Work/qemu.git/exec.c:2621
> > #21 0x000055af0a3be6cb in address_space_write (as=0x55af0aedede0
> > <address_space_io>, addr=49458, attrs=..., buf=0x7f6110aa0000 "\a", len=1)
> > at /net/gimli/home/alwillia/Work/qemu.git/exec.c:2666
> > #22 0x000055af0a3bea57 in address_space_rw (as=0x55af0aedede0
> > <address_space_io>, addr=49458, attrs=..., buf=0x7f6110aa0000 "\a", len=1,
> > is_write=true)
> > at /net/gimli/home/alwillia/Work/qemu.git/exec.c:2768
> > #23 0x000055af0a40c8d7 in kvm_handle_io (port=49458, attrs=...,
> > data=0x7f6110aa0000, direction=1, size=1, count=1) at
> > /net/gimli/home/alwillia/Work/qemu.git/kvm-all.c:1800
> > #24 0x000055af0a40cddd in kvm_cpu_exec (cpu=0x55af0b9c33f0) at
> > /net/gimli/home/alwillia/Work/qemu.git/kvm-all.c:1958
> > #25 0x000055af0a3f3c58 in qemu_kvm_cpu_thread_fn (arg=0x55af0b9c33f0) at
> > /net/gimli/home/alwillia/Work/qemu.git/cpus.c:998
> > #26 0x00007f60f5bc05ca in start_thread (arg=0x7f60e4ce9700) at
> > pthread_create.c:333
> > #27 0x00007f60f58fa0ed in clone () at
> > ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
> >
> > If I'm applying it to the wrong place, let me know. Thanks,
> >
> > Alex
> >
> >> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> >> index 131f164..a8b5ab8 100644
> >> --- a/hw/virtio/vhost.c
> >> +++ b/hw/virtio/vhost.c
> >> @@ -1186,17 +1186,14 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
> >> int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
> >> {
> >> BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> >> - VirtioBusState *vbus = VIRTIO_BUS(qbus);
> >> - VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
> >> int i, r, e;
> >>
> >> - if (!k->ioeventfd_assign) {
> >> + r = virtio_device_grab_ioeventfd(vdev);
> >> + if (r < 0) {
> >> error_report("binding does not support host notifiers");
> >> - r = -ENOSYS;
> >> goto fail;
> >> }
> >>
> >> - virtio_device_stop_ioeventfd(vdev);
> >> for (i = 0; i < hdev->nvqs; ++i) {
> >> r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index
> >> + i,
> >> true);
> >> @@ -1216,7 +1213,7 @@ fail_vq:
> >> }
> >> assert (e >= 0);
> >> }
> >> - virtio_device_start_ioeventfd(vdev);
> >> + virtio_device_release_ioeventfd(vdev);
> >> fail:
> >> return r;
> >> }
> >> @@ -1239,7 +1236,7 @@ void vhost_dev_disable_notifiers(struct vhost_dev
> >> *hdev, VirtIODevice *vdev)
> >> }
> >> assert (r >= 0);
> >> }
> >> - virtio_device_start_ioeventfd(vdev);
> >> + virtio_device_release_ioeventfd(vdev);
> >> }
> >>
> >> /* Test and clear event pending status.
> >> diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
> >> index bf61f66..42467f1 100644
> >> --- a/hw/virtio/virtio-bus.c
> >> +++ b/hw/virtio/virtio-bus.c
> >> @@ -147,6 +147,38 @@ void virtio_bus_set_vdev_config(VirtioBusState *bus,
> >> uint8_t *config)
> >> }
> >> }
> >>
> >> +int virtio_bus_grab_ioeventfd(VirtioBusState *bus)
> >> +{
> >> + VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
> >> +
> >> + /* vhost can be used even if ioeventfd=off in the proxy device,
> >> + * so do not check k->ioeventfd_enabled.
> >> + */
> >> + if (!k->ioeventfd_assign) {
> >> + return -ENOSYS;
> >> + }
> >> +
> >> + if (bus->ioeventfd_grabbed == 0 && bus->ioeventfd_started) {
> >> + virtio_bus_stop_ioeventfd(bus);
> >> + /* Remember that we need to restart ioeventfd
> >> + * when ioeventfd_grabbed becomes zero.
> >> + */
> >> + bus->ioeventfd_started = true;
> >> + }
> >> + bus->ioeventfd_grabbed++;
> >> + return 0;
> >> +}
> >> +
> >> +void virtio_bus_release_ioeventfd(VirtioBusState *bus)
> >> +{
> >> + assert(bus->ioeventfd_grabbed != 0);
> >> + if (--bus->ioeventfd_grabbed == 0 && bus->ioeventfd_started) {
> >> + /* Force virtio_bus_start_ioeventfd to act. */
> >> + bus->ioeventfd_started = false;
> >> + virtio_bus_start_ioeventfd(bus);
> >> + }
> >> +}
> >> +
> >> int virtio_bus_start_ioeventfd(VirtioBusState *bus)
> >> {
> >> VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
> >> @@ -161,10 +193,12 @@ int virtio_bus_start_ioeventfd(VirtioBusState *bus)
> >> if (bus->ioeventfd_started) {
> >> return 0;
> >> }
> >> - r = vdc->start_ioeventfd(vdev);
> >> - if (r < 0) {
> >> - error_report("%s: failed. Fallback to userspace (slower).",
> >> __func__);
> >> - return r;
> >> + if (!bus->ioeventfd_grabbed) {
> >> + r = vdc->start_ioeventfd(vdev);
> >> + if (r < 0) {
> >> + error_report("%s: failed. Fallback to userspace (slower).",
> >> __func__);
> >> + return r;
> >> + }
> >> }
> >> bus->ioeventfd_started = true;
> >> return 0;
> >> @@ -179,9 +213,11 @@ void virtio_bus_stop_ioeventfd(VirtioBusState *bus)
> >> return;
> >> }
> >>
> >> - vdev = virtio_bus_get_device(bus);
> >> - vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
> >> - vdc->stop_ioeventfd(vdev);
> >> + if (!bus->ioeventfd_grabbed) {
> >> + vdev = virtio_bus_get_device(bus);
> >> + vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
> >> + vdc->stop_ioeventfd(vdev);
> >> + }
> >> bus->ioeventfd_started = false;
> >> }
> >>
> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >> index bcbcfe0..89b0b80 100644
> >> --- a/hw/virtio/virtio.c
> >> +++ b/hw/virtio/virtio.c
> >> @@ -2202,6 +2202,22 @@ void virtio_device_stop_ioeventfd(VirtIODevice
> >> *vdev)
> >> virtio_bus_stop_ioeventfd(vbus);
> >> }
> >>
> >> +int virtio_device_grab_ioeventfd(VirtIODevice *vdev)
> >> +{
> >> + BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
> >> + VirtioBusState *vbus = VIRTIO_BUS(qbus);
> >> +
> >> + return virtio_bus_grab_ioeventfd(vbus);
> >> +}
> >> +
> >> +void virtio_device_release_ioeventfd(VirtIODevice *vdev)
> >> +{
> >> + BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
> >> + VirtioBusState *vbus = VIRTIO_BUS(qbus);
> >> +
> >> + virtio_bus_release_ioeventfd(vbus);
> >> +}
> >> +
> >> static void virtio_device_class_init(ObjectClass *klass, void *data)
> >> {
> >> /* Set the default value here. */
> >> diff --git a/include/hw/virtio/virtio-bus.h
> >> b/include/hw/virtio/virtio-bus.h
> >> index fdf7fda..8a51e2c 100644
> >> --- a/include/hw/virtio/virtio-bus.h
> >> +++ b/include/hw/virtio/virtio-bus.h
> >> @@ -97,6 +97,16 @@ struct VirtioBusState {
> >> * Set if ioeventfd has been started.
> >> */
> >> bool ioeventfd_started;
> >> +
> >> + /*
> >> + * Set if ioeventfd has been grabbed by vhost. When ioeventfd
> >> + * is grabbed by vhost, we track its started/stopped state (which
> >> + * depends in turn on the virtio status register), but do not
> >> + * register a handler for the ioeventfd. When ioeventfd is
> >> + * released, if ioeventfd_started is true we finally register
> >> + * the handler so that QEMU's device model can use ioeventfd.
> >> + */
> >> + int ioeventfd_grabbed;
> >> };
> >>
> >> void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp);
> >> @@ -131,6 +141,10 @@ bool virtio_bus_ioeventfd_enabled(VirtioBusState
> >> *bus);
> >> int virtio_bus_start_ioeventfd(VirtioBusState *bus);
> >> /* Stop the ioeventfd. */
> >> void virtio_bus_stop_ioeventfd(VirtioBusState *bus);
> >> +/* Tell the bus that vhost is grabbing the ioeventfd. */
> >> +int virtio_bus_grab_ioeventfd(VirtioBusState *bus);
> >> +/* bus that vhost is not using the ioeventfd anymore. */
> >> +void virtio_bus_release_ioeventfd(VirtioBusState *bus);
> >> /* Switch from/to the generic ioeventfd handler */
> >> int virtio_bus_set_host_notifier(VirtioBusState *bus, int n, bool assign);
> >>
> >> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> >> index ac65d6a..35ede30 100644
> >> --- a/include/hw/virtio/virtio.h
> >> +++ b/include/hw/virtio/virtio.h
> >> @@ -270,6 +270,8 @@ void
> >> virtio_queue_set_guest_notifier_fd_handler(VirtQueue *vq, bool assign,
> >> bool with_irqfd);
> >> int virtio_device_start_ioeventfd(VirtIODevice *vdev);
> >> void virtio_device_stop_ioeventfd(VirtIODevice *vdev);
> >> +int virtio_device_grab_ioeventfd(VirtIODevice *vdev);
> >> +void virtio_device_release_ioeventfd(VirtIODevice *vdev);
> >> bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev);
> >> EventNotifier *virtio_queue_get_host_notifier(VirtQueue *vq);
> >> void virtio_queue_host_notifier_read(EventNotifier *n);
> >
