qemu/hw/virtio
Paolo Bonzini 310837de6c virtio: introduce grab/release_ioeventfd to fix vhost
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 <felipe@nutanix.com>
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reported-by: Alex Williamson <alex.williamson@redhat.com>
Fixes: ed08a2a0b ("virtio: use virtio_bus_set_host_notifier to start/stop ioeventfd")
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Tested-by: Farhan Ali <alifm@linux.vnet.ibm.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2016-11-18 17:29:25 +02:00
..
Makefile.objs virtio-crypto-pci: add virtio crypto pci support 2016-11-01 19:21:08 +02:00
trace-events trace: move hw/virtio/virtio-balloon.c trace points into correct file 2016-09-28 19:17:55 +01:00
vhost-backend.c vhost-vsock: add virtio sockets device 2016-09-10 00:28:08 +03:00
vhost-user.c char: use qemu_chr_fe* functions with CharBackend argument 2016-10-24 15:27:21 +02:00
vhost-vsock.c virtio: cleanup VMSTATE_VIRTIO_DEVICE 2016-10-10 02:21:43 +03:00
vhost.c virtio: introduce grab/release_ioeventfd to fix vhost 2016-11-18 17:29:25 +02:00
virtio-balloon.c virtio: rename virtqueue_discard to virtqueue_unpop 2016-11-15 17:20:36 +02:00
virtio-bus.c virtio: introduce grab/release_ioeventfd to fix vhost 2016-11-18 17:29:25 +02:00
virtio-crypto-pci.c virtio-crypto: tag as not hotpluggable and migration 2016-11-15 17:20:36 +02:00
virtio-crypto.c virtio-crypto: fix virtio_queue_set_notification() race 2016-11-18 17:14:10 +02:00
virtio-mmio.c virtio: introduce virtio_device_ioeventfd_enabled 2016-10-30 19:51:32 +02:00
virtio-pci.c virtio: allow per-device-class legacy features 2016-11-15 17:20:36 +02:00
virtio-pci.h virtio-crypto-pci: add virtio crypto pci support 2016-11-01 19:21:08 +02:00
virtio-rng.c virtio: cleanup VMSTATE_VIRTIO_DEVICE 2016-10-10 02:21:43 +03:00
virtio.c virtio: introduce grab/release_ioeventfd to fix vhost 2016-11-18 17:29:25 +02:00