** Description changed: [Impact] TLDR; It is not currently possible to define a libvirt KVM guest that will boot on any arm64 system. This breaks assumptions of higher level tools like nova and virt-install. ARM systems can only boot KVM guests that have the same GIC (Generic Interrupt Controller) version as the host. GICv2 is the QEMU default but, if your system does not have a GICv2, you need to know your GIC version and pass that down to the QEMU command line (e.g. -M virt,gic_version=3). If you (or your tools) don't know to do that, your guests will just fail to boot on non-GICv2 hosts with the obscure error "Failed to set device address: No such device". Starting with Ubuntu 16.04, we support at least one GICv3-only system (Cavium ThunderX). I consider this a hardware enablement issue, and seek SRU approval based on that criteria. Recent changes to QEMU and libvirt have improved this situation. QEMU now exposes a "query-gic-capabilities" QMP interface that can let the caller ask what GIC types are available for guests to use on that host. libvirt can now make use of this QEMU interface, and expose that information to users via the domcapabilities interface. Further, the user can specify a gic version of "host" to have libvirt choose a detected GIC version, or the user can omit the <gic> feature altogether, and libvirt will choose a GIC version supported by the host and update the guest XML appropriately. This allows tools like virt-install and nova to generate GIC-agnostic XML that can boot on any arm64 host. [Test Case] Detection. Run this command on an arm64 host: $ sudo virsh domcapabilities --machine virt --virttype kvm After the update, you should see a <gic> capability with a list of supported GIC versions that match the host system. Runtime1. Place the attached gic.xml file in /etc/libvirt/qemu. $ sudo virsh define /etc/libvirt/qemu/gic.xml - $ sudo virsh start /etc/libvirt/qemu/gic.xml + $ sudo virsh start gic Prior to this update, it will error out with: error: XML error: malformed gic version: host After the update, it'll boot using whatever GIC version is available on your system. Runtime2. On a GICv3 system, edit the gic.xml file and remove the <gic version='host'/> line. $ sudo virsh define /etc/libvirt/qemu/gic.xml $ sudo virsh start /etc/libvirt/qemu/gic.xml Prior to this update, this will fail with an I/O error. After this update, it will succeed, and a <gic version='3'/> setting will be added to the XML. [Regression Risk] These patches are all upstream, so risk on this patchset should be low. The change to both QEMU and libvirt are backwards compatible with the existing versions in xenial. If no GIC version is specified, QEMU still defaults to GICv2. If a GIC is specified w/o a version, libvirt continues to default to GICv2.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1566564 Title: support query-gic-version QMP command To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1566564/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
