On Fri, Nov 18, 2016 at 09:15:32AM +0100, Christian Borntraeger wrote: > On 11/16/2016 07:05 PM, Paolo Bonzini 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] > > > As this seems to fix a functional issues, is there any chance to apply this > patch now and not wait for the discussion about patch 2 and 3 to calm down?
It's in my tree, will be in the next pull.