From f2b8609d48352739d33fba4ed950c3920a9a5c94 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Tue, 12 Sep 2017 15:28:03 +0100 Subject: [PATCH] vhost: Release memory references on cleanup RH-Author: Alex Williamson Message-id: <20170912152739.22790.48279.stgit@redhat.home> Patchwork-id: 76315 O-Subject: [RHEL-7.4.z qemu-kvm-rhev PATCH 1/1] vhost: Release memory references on cleanup Bugzilla: 1490742 RH-Acked-by: Paolo Bonzini RH-Acked-by: Auger Eric RH-Acked-by: John Snow vhost registers a MemoryListener where it adds and removes references to MemoryRegions as the MemoryRegionSections pass through. The region_add callback is invoked for each existing section when the MemoryListener is registered, but unregistering the MemoryListener performs no reciprocal region_del callback. It's therefore the owner of the MemoryListener's responsibility to cleanup any persistent changes, such as these memory references, after unregistering. The consequence of this bug is that if we have both a vhost device and a vfio device, the vhost device will reference any mmap'd MMIO of the vfio device via this MemoryListener. If the vhost device is then removed, those references remain outstanding. If we then attempt to remove the vfio device, it never gets finalized and the only way to release the kernel file descriptors is to terminate the QEMU process. Fixes: dfde4e6e1a86 ("memory: add ref/unref calls") Cc: Michael S. Tsirkin Cc: Paolo Bonzini Cc: qemu-stable@nongnu.org # v1.6.0+ Signed-off-by: Alex Williamson Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin (cherry picked from commit ee4c112846a0f2ac4fe5601918b0a2642ac8e2ed) Signed-off-by: Danilo C. L. de Paula --- hw/virtio/vhost.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index 748e331..9ed2132 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -1356,6 +1356,10 @@ void vhost_dev_cleanup(struct vhost_dev *hdev) if (hdev->mem) { /* those are only safe after successful init */ memory_listener_unregister(&hdev->memory_listener); + for (i = 0; i < hdev->n_mem_sections; ++i) { + MemoryRegionSection *section = &hdev->mem_sections[i]; + memory_region_unref(section->mr); + } QLIST_REMOVE(hdev, entry); } if (hdev->migration_blocker) { -- 1.8.3.1