6b7f87d7f1
virHostdevReattachPCIDevice() is a static that simply does a wait loop with virPCIDeviceWaitForCleanup() before calling virPCIDeviceReattach(). This loop traces back to commit d1e5676c0d, aiming to solve a race condition between Libvirt returning the device back to the host and QEMU trying to access it in the meantime, which resulted in QEMU exiting on error and killing the guest. This happens because device_del is asynchronous, returning OK even if the guest didn't release the device. Commit 01abc8a1b8 moved this code to qemu_hostdev.c, 82e8dd4cf8 added the pci-stub conditional for the loop, 899b261127 moved the code to virhostdev.c where it stood until now. The intent of this wait loop is still valid: device_del is still not bullet proof into preventing the conditions that commit d1e5676c0d aimed to fix, especially when considering all the architectures we must support. However, this loop is executed only in virHostdevReattachPCIDevice(), leaving every other virPCIDeviceReattach() call prone to that error. Let's move the wait loop code to virPCIDeviceReattach(). This will: - make every reattach call safe from this race condition with the pci-stub; - allow for a bit of code cleanup (virHostdevReattachPCIDevice() can be erased, and virHostdevReAttachPCIDevices() can use virPCIDeviceReattach() directly); - make it easier to understand the overall reattach mechanisms in Libvirt, without the risk of a newcomer wondering why reattach is done slightly different in some instances. Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> Reviewed-by: Michal Privoznik <mprivozn@redhat.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: