75dd595861
When connecting to qemu's monitor the @vm object is unlocked. This is justified - connecting may take a long time and we don't want to wait with the domain object locked. However, just before the domain object is locked again, the monitor's FD is registered in the event loop. Therefore, there is a small window where the event loop has a chance to call a handler for an event that occurred on the monitor FD but vm is not initalized properly just yet (i.e. priv->mon is not set). For instance, if there's an incoming migration, qemu creates its socket but then fails to initialize (for various reasons, I'm reproducing this by using hugepages but leaving the HP pool empty) then the following may happen: 1) qemuConnectMonitor() unlocks @vm 2) qemuMonitorOpen() connects to the monitor socket and by calling qemuMonitorOpenInternal() which subsequently calls qemuMonitorRegister() the event handler is installed 3) qemu fails to initialize and exit()-s, which closes the monitor 4) The even loop sees EOF on the monitor and the control gets to qemuProcessEventHandler() which locks @vm and calls processMonitorEOFEvent() which then calls qemuMonitorLastError(priv->mon). But priv->mon is not set just yet. 5) qemuMonitorLastError() dereferences NULL pointer The solution is to unlock the domain object for a shorter time and most importantly, register event handler with domain object locked so that any possible event processing is done only after @vm's private data was properly initialized. This issue is also mentioned in v4.2.0-99-ga5a777a8ba. Since we are unlocking @vm and locking it back, another thread might have destroyed the domain meanwhile. Therefore we have to check if domain is still active, and we have to do it at the same place where domain lock is acquired back, i.e. in qemuMonitorOpen(). This creates a small problem for our test suite which calls qemuMonitorOpen() directly and passes @vm which has no definition. This makes virDomainObjIsActive() call crash. Fortunately, allocating empty domain definition is sufficient. Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Libvirt API for virtualization
Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
For some of these hypervisors, it provides a stateful management daemon which runs on the virtualization host allowing access to the API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other languages including Python, Perl, PHP, Go, Java, OCaml, as well as mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the website:
License
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.0 (or later). See the files COPYING.LESSER
and COPYING for full license terms & conditions.
Installation
Libvirt uses the GNU Autotools build system, so in general can be built and installed with the usual commands. For example, to build in a manner that is suitable for installing as root, use:
$ ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ ./configure --prefix=$HOME/usr
$ make
$ make install
The libvirt code relies on a large number of 3rd party libraries. These will
be detected during execution of the configure script and a summary printed
which lists any missing (optional) dependencies.
Contributing
The libvirt project welcomes contributions in many ways. For most components the best way to contribute is to send patches to the primary development mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
The libvirt project has two primary mailing lists:
- libvirt-users@redhat.com (for user discussions)
- libvir-list@redhat.com (for development only)
Further details on contacting the project are available on the website: