[Qemu-devel] [PATCH for-2.11] vfio: Fix vfio-kvm group registration

[Alex Williamson <alex.williamson@redhat.com>]

Commit 8c37faa475f3 ("vfio-pci, ppc64/spapr: Reorder group-to-container
attaching") moved registration of groups with the vfio-kvm device from
vfio_get_group() to vfio_connect_container(), but it missed the case
where a group is attached to an existing container and takes an early
exit.  Perhaps this is a less common case on ppc64/spapr, but on x86
(without viommu) all groups are connected to the same container and
thus only the first group gets registered with the vfio-kvm device.
This becomes a problem if we then hot-unplug the devices associated
with that first group and we end up with KVM being misinformed about
any vfio connections that might remain.  Fix by including the call to
vfio_kvm_device_add_group() in this early exit path.

Fixes: 8c37faa475f3 ("vfio-pci, ppc64/spapr: Reorder group-to-container attaching")
Cc: qemu-stable@nongnu.org # qemu-2.10+
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

This bug also existed in QEMU 2.10, but I think the fix is sufficiently
obvious (famous last words) to propose for 2.11 at this late date.  If
the first group is hot unplugged then KVM may revert to code emulation
that assumes no non-coherent DMA is present on some systems.  Also for
KVMGT, if the vGPU is not the first device registered, then the
notifier to enable linkages to KVM would not be called.  Please review.
Thanks,

Alex

 hw/vfio/common.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 7b2924c0ef19..7007878e345e 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -968,6 +968,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
         if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {
             group->container = container;
             QLIST_INSERT_HEAD(&container->group_list, group, container_next);
+            vfio_kvm_device_add_group(group);
             return 0;
         }
     }