Bug 1489670

Summary:	Hot-unplugging a vhost network device leaks references to VFIOPCIDevice's
Product:	Red Hat Enterprise Linux 7	Reporter:	Sergio Lopez <slopezpa>
Component:	qemu-kvm-rhev	Assignee:	Alex Williamson <alex.williamson>
Status:	CLOSED ERRATA	QA Contact:	Yanan Fu <yfu>
Severity:	high	Docs Contact:
Priority:	high
Version:	7.3	CC:	alex.williamson, chayang, jen, jherrman, jinzhao, jjung, juzhang, knoel, michen, mrezanin, pezhang, rhodain, slopezpa, virt-maint, xiywang, yfu
Target Milestone:	rc	Keywords:	ZStream
Target Release:	---
Hardware:	x86_64
OS:	Unspecified
Whiteboard:
Fixed In Version:	qemu-kvm-rhev-2.10.0-2.el7	Doc Type:	Bug Fix
Doc Text:	Hot-unplugging Virtual Function I/O (VFIO) devices previously failed when performed after hot-unplugging a vhost network device. This update fixes the underlying code, and the VFIO device is unplugged correctly in the described circumstances.	Story Points:	---
Clone Of:
Clones:	1490742 (view as bug list)		Environment:
Last Closed:	2018-04-11 00:33:01 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1490742

Description Sergio Lopez 2017-09-08 05:42:55 UTC

Hot-unplugging a vhost network device leaks references to VFIOPCIDevice's. This causes that, when trying to hot-unplug one of those VFIO devices, QEMU can't finalize it properly because the references never reach 0.

So far, we've identified the following scenarios (100% reproducible):

---
 1. Start a VM with both a VIRTIO network device and a VFIO hostdev.
 2. Hot-unplug the VIRTIO device.
 3. Hot-unplug the VFIO -> QEMU can't finalize the device: ref=2
---
 1. Start a VM with just a VFIO hostdev.
 2. Hot-plug the VIRTIO device.
 3. Hot-unplug the VFIO -> QEMU can't finalize the device: ref=2
---
 1. Start a VM with just a VFIO hostdev.
 2. Hot-plug the VIRTIO device.
 3. Hot-unplug the VIRTIO device.
 4. Hot-unplug the VFIO -> QEMU can't finalize the device: ref=2
---

There's a patch for this posted in QEMU's mailing list:

 - http://lists.nongnu.org/archive/html/qemu-devel/2017-09/msg01787.html

Comment 16 Miroslav Rezanina 2017-10-13 10:26:23 UTC

Fix included in qemu-kvm-rhev-2.10.0-2.el7

Comment 20 errata-xmlrpc 2018-04-11 00:33:01 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2018:1104