On Wed, 16 Nov 2016 19:05:49 +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> > Message-Id: <20161111192855.26350-1-pbonz...@redhat.com> > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > --- > v1->v2: more comments [Cornelia] > > hw/virtio/vhost.c | 14 +++++----- > hw/virtio/virtio-bus.c | 58 > ++++++++++++++++++++++++++++++++++-------- > hw/virtio/virtio.c | 16 ++++++++++++ > include/hw/virtio/virtio-bus.h | 14 ++++++++++ > include/hw/virtio/virtio.h | 2 ++ > 5 files changed, 86 insertions(+), 18 deletions(-) Reviewed-by: Cornelia Huck <cornelia.h...@de.ibm.com>