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Consider a host with 8 CPUs. There are the following possible scenarios 1. Bare metal; libvirtd has affinity of 8 CPUs; QEMU should get 8 CPUs 2. Bare metal; libvirtd has affinity of 2 CPUs; QEMU should get 8 CPUs 3. Container has affinity of 8 CPUs; libvirtd has affinity of 8 CPus; QEMU should get 8 CPUs 4. Container has affinity of 8 CPUs; libvirtd has affinity of 2 CPus; QEMU should get 8 CPUs 5. Container has affinity of 4 CPUs; libvirtd has affinity of 4 CPus; QEMU should get 4 CPUs 6. Container has affinity of 4 CPUs; libvirtd has affinity of 2 CPus; QEMU should get 4 CPUs Scenarios 1 & 2 always work unless systemd restricted libvirtd privs. Scenario 3 works because libvirt checks current affinity first and skips the sched_setaffinity call, avoiding the SYS_NICE issue Scenario 4 works only if CAP_SYS_NICE is availalbe Scenarios 5 & 6 works only if CAP_SYS_NICE is present *AND* the cgroups cpuset is not set on the container. If libvirt blindly ignores the sched_setaffinity failure, then scenarios 4, 5 and 6 should all work, but with caveat in case 4 and 6, that QEMU will only get 2 CPUs instead of the possible 8 and 4 respectively. This is still better than failing. Therefore libvirt can blindly ignore the setaffinity failure, but *ONLY* ignore it when there was no affinity specified in the XML config. If user specified affinity explicitly, libvirt must report an error if it can't be honoured. Resolves: https://bugzilla.redhat.com/1819801 Suggested-by: Daniel P. Berrangé <berrange@redhat.com> Signed-off-by: Martin Kletzander <mkletzan@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@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
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
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: