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CPU features/flags - host vs. guest (Libvirt/QEMU/KVM)
by kAja Ziegler 07 Sep '22

07 Sep '22

Hello, does anyone know of any list/table (ideally as up-to-date as possible) with individual CPU features/flags for x86_64 (preferably Intel), which would state: - description of individual features/flags - dependencies between individual features/flags - e.g. avx on xsave - what features/flags are checked on the hypervisor (host), but are not propagated to the guest - e.g. acpi, ds, monitor, pbe, tm, etc. - some are masked/disabled [(not) supported] by Libvirt, others by KVM/QEMU - what features/flags active for/in the guest limit certain virtualization behavior/options such as live migration - e.g. invtsc, xsaves - so far I only found https://github.com/libvirt/libvirt/blob/master/src/cpu_map/x86_features.xml - features with migratable='no' I would like to tweak the CPU configuration for the virtual servers ie. choose the basic CPU model and turn on/off the necessary or appropriate features/flags while maintaining the possibility of live migration. But I miss the above-mentioned contexts, because not all the mentioned features within the cpu element in the VM definition (domains in Libvirt) are then visible inside the VM in /proc/cpuinfo. Of course, I know about other related commands, registers, etc. like "virsh capabilities|cpu-baseline|cpu-compare", MSR, fixes in CPU microcode, host-model or host-passthrough CPU... but I'm still not sure about setting the match, check and fallback attributes and the resulting behavior of Libvirt and QEMU/KVM. Many thanks in advance for any response K. Ziegler

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Libvirtd slower over time
by André Malm 29 Aug '22

29 Aug '22

Hello, I have some issues with libvirtd getting slow over time. After a fresh reboot (or systemctl restart libvirtd) virsh list / virt-install is fast, as expected, but after a couple of months uptime they both take a significantly longer time. Virsh list takes around 3 seconds (from 0.04s on a fresh reboot) and virt-install takes over a minute (from around a second). Running strace on virsh list it seems to get stuck in a loop on this: poll([{fd=5<socket:[173169773]>, events=POLLOUT}, {fd=6<anon_inode:[eventfd]>, events=POLLIN}], 2, -1) = 2 ([{fd=5, revents=POLLOUT}, {fd=6, revents=POLLIN}]) While restarting libvirtd fixes it a restart takes around 1 minute where ebtables rules etc are recreated and it does interrupt the service. What could cause this? How would I troubleshoot this? I'm running Ubuntu 22.04 / libvirt 8.0.0 with 70 active VM’s on a 16/32 core machine with 256GB of ram, CPU is below 50% usage at all times, memory below 50% usage and swap 0% usage. Thanks, André

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Libvirt web application
by Callie Martin 25 Aug '22

25 Aug '22

Hello, We received the following message on Red Hat's Twitter account. Can anyone on this list confirm if libvirt-users(a)redhat.com is 1) active and 2) the right contact information for this user to reach out to? [image: image.png] Thanks, -- Callie Martin She / Her / Hers Manager, Social Media Red Hat <https://www.redhat.com/> 100 E. Davie St. Raleigh, NC calmarti(a)redhat.com M: 919-630-7721 | T: 919-890-8011 @RedHat <https://twitter.com/redhat> Red Hat <https://www.linkedin.com/company/red-hat> Red Hat <https://www.facebook.com/RedHatInc> <https://red.ht/sig>

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NUMA node - Memory Only
by Jin Huang 22 Aug '22

22 Aug '22

Hi, libvirt-users How could I set up a memory-only and no-cpu NUMA node for the qemu-VM with the XML file? Seems each NUMA cell has to be bundled with some specific cpuids. If I write the element like this, it is wrong. <cpu mode='host-passthrough'> <numa> <cell id='0' cpus='0-3' memory='16' unit='GiB'/> <cell id='1' cpus='*null*' memory='16' unit='GiB'/> </numa> </cpu> Also if I ignore the cpus item, it is not acceptable for the virsh command. The reason I want the memory-only node is that I want to set up multiple memory tiers for the VM, just like https://stevescargall.com/2022/06/10/using-linux-kernel-memory-tiering/ Thank You Best Jin Huang

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Memory locking limit and zero-copy migrations
by Milan Zamazal 19 Aug '22

19 Aug '22

Hi, do I read libvirt sources right that when <memtune> is not used in the libvirt domain then libvirt takes proper care about setting memory locking limits when zero-copy is requested for a migration? I also wonder whether there are any other situations where memory limits could be set by libvirt or QEMU automatically rather than having no memory limits? We had oVirt bugs in the past where certain VMs with VFIO devices couldn't be started due to extra requirements on the amount of locked memory and adding <hard_limit> to the domain apparently helped. Thanks, Milan

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Problem with a disk device of type 'volume'
by Frédéric Lespez 18 Aug '22

18 Aug '22

Hi, I need some help to debug a problem with libvirt and a disk device of type 'volume'. I have a VM failing to start with the following error : $ virsh -c qemu:///system start server error :Failed to start domain 'server' error :internal error: process exited while connecting to monitor: 2022-08-13T09:26:50.121259Z qemu-system-x86_64: -blockdev {"driver":"file","filename":"/mnt/images/debian-11-genericcloud-amd64.qcow2","node-name":"libvirt-3-storage","auto-read-only":true,"discard":"unmap"}: Could not open '/mnt/images/debian-11-genericcloud-amd64.qcow2': Permission denied I check the file access permission, but they are correct. I try to set everything to 777 or run qemu as root, but the problem persist. $ ll -d /mnt /mnt/images /mnt/images/* drwxr-xr-x 9 root root 4,0K 31 déc. 2021 /mnt drwxr-xr-x 2 root root 4,0K 13 août 11:31 /mnt/images -rw-r--r-- 1 libvirt-qemu libvirt-qemu 242M 13 août 11:31 /mnt/images/debian-11-genericcloud-amd64.qcow2 -rw-r--r-- 1 libvirt-qemu libvirt-qemu 366K 13 août 11:31 /mnt/images/server_cloudinit.iso -rw-r--r-- 1 libvirt-qemu libvirt-qemu 593M 13 août 11:59 /mnt/images/server_image.qcow2 After a lot of searching and testing, I found out that the disk device definition is linked to the source of the problem. The disk device is defined like this : <disk type="volume" device="disk"> <driver name="qemu" type="qcow2"/> <source pool="TERRAFORM" volume="server_image.qcow2"/> <target dev="vda" bus="virtio"/> <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x0"/> </disk> This image 'server_image.qcow2' use a backing file: $ qemu-img info /mnt/images/server_image.qcow2 --backing-chain image: /mnt/stockage_rapide/VMs/terraform/puppetdev_server_image.qcow2 file format: qcow2 virtual size: 6 GiB (6442450944 bytes) disk size: 475 MiB cluster_size: 65536 backing file: /mnt/images/debian-11-genericcloud-amd64.qcow2 backing file format: qcow2 Format specific information: compat: 0.10 compression type: zlib refcount bits: 16 image: /mnt/images/debian-11-genericcloud-amd64.qcow2 file format: qcow2 virtual size: 2 GiB (2147483648 bytes) disk size: 242 MiB cluster_size: 65536 Format specific information: compat: 1.1 compression type: zlib lazy refcounts: false refcount bits: 16 corrupt: false extended l2: false And here is the definition of the associated storage pool : <pool type="dir"> <name>TERRAFORM</name> <uuid>dae00836-db4d-49ba-9d32-1f0278055516</uuid> <capacity unit="bytes">155674652672</capacity> <allocation unit="bytes">74396299264</allocation> <available unit="bytes">81278353408</available> <source> </source> <target> <path>/mnt/images</path> <permissions> <mode>0755</mode> <owner>0</owner> <group>0</group> </permissions> </target> </pool> If I changed the disk device definition to this (and changing only that), the domain start and works fine (no permission problem !). <disk type="file" device="disk"> <driver name="qemu" type="qcow2"/> <source file="/mnt/images/server_image.qcow2"/> <target dev="vda" bus="virtio"/> <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x0"/> </disk> Could you help me find the reason why the domain doesn't work when the disk device is of type 'volume' ? Thanks in advance for your help. Regards, Fred Additional information: - Running this on Debian 11 with libvirt 8.0.0 (from backports) and qemu 7.0 (from backports). - Vanilla configuration of libvirt. I have just added my regular user to the libvirt group. - Problem exists even if AppArmor is disabled. PS: I want to use a disk device of type 'volume' because this domain is created by Terraform using the libvirt provider which use this kind of disk since it has some advantages. See the details here : https://github.com/dmacvicar/terraform-provider-libvirt/issues/126#issuecom…

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Libvirt virsh : Error starting network, cannot execute binary /usr/sbin/iptables
by Pascal 17 Aug '22

17 Aug '22

Hi, I am a bit lost and hope someone can help me. I am running Debian bookworm (testing) with last updates. $ sudo apt policy libvirt-daemon libvirt-daemon: Installé : 8.5.0-1 Candidat : 8.5.0-1 Table de version : *** 8.5.0-1 100 100 /var/lib/dpkg/status I am unable to start default network , and get an error related to iptables : $ sudo virsh net-start default erreur :Impossible de démarrer le réseau default erreur :internal error: Failed to apply firewall rules /usr/sbin/iptables -w --table filter --list-rules: libvirt: erreur : cannot execute binary /usr/sbin/iptables: Aucun fichier ou dossier de ce type Sorry for the french, it says "impossible to start default network" and "no such file or folder" at the end. It is true I removed iptables because I want to use only nftables (I removed both ufw and iptables packages (apt remove), and enabled the nftables service before error raises). Before this, all was fine, but when I enabled nftables, all VMs disapeared from virt-manager). I uninstalled KVM related packages and reinstalled, still the same. I also installed back iptables, but strangely I still get the same error, although binary /usr/sbin/iptables is there. I tried many things with no luck, restarted libvirtd service, recreated the network, etc... Has anyone some idea about what is happening here ? is there some incompatibility with nftables (firewalld service is disabled) and libvirt ? Thank you, Pascal

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libvirt can't setup simple bridged network?
by Ian Pilcher 15 Aug '22

15 Aug '22

I feel like I'm taking crazy pills! I'm reading the libvirt network XML format documentation[1], and I can't figure out how to create a simple bridged network - no NAT, no routing, no OVS, no macvtap, etc. I.e., just a Linux bridge with a single physical interface attached. None of the 3 scenarios listed for <forward mode='bridge'> describe the simple setup that I'm trying to create, so it looks like I'll need to create the bridge separately. (It's not hard to do, it just seems like such a weird gap the in the functionality.) [1] https://libvirt.org/formatnetwork.html -- ======================================================================== Google Where SkyNet meets Idiocracy ========================================================================

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New functionality in virt-install
by O'Reilly, Michael 09 Aug '22

09 Aug '22

Hi libvirt-users, I've been tracking the progress of this patch https://listman.redhat.com/archives/libvir-list/2022-August/233328.html to enable SGX support in libvirt. My question is this. Who is responsible for ensuring that new functionality like SGX is also supported by virt-install? Is it part of the commit process to ensure virt-install can use the new functionality in libvirt, or is it up to the virt-manager community to track changes. And maybe this is a question for the virt-tools-list(a)redhat.com list also? Some guidance would be appreciated. Regards Michael OR -------------------------------------------------------------- Intel Research and Development Ireland Limited Registered in Ireland Registered Office: Collinstown Industrial Park, Leixlip, County Kildare Registered Number: 308263 This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.

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Can RHEL7 VM run remote commands to Fedora36 host?
by Carol Bouchard 01 Aug '22

01 Aug '22

I have a Fedora36 laptop which hosts VMs with RHEL7 using libvirt. One of the RHEL7 VMs, runs remote commands (as root) to 'start' another VM by way of my laptop. In other words, the following command is run: virsh --connect 'qemu+ssh://192.168.120.1/system' start beaker-test-vm1.beaker If I run non-remote version of the command on the laptop, it is successful. For example, virsh --connect qemu:///system start beaker-test-vm1.beaker <-- Successful on laptop. If I do a query like the following *(notice socket use)*, it is successful. virsh -d0 --connect 'qemu+ssh://192.168.120.1/system?*socket*=/var/run/libvirt/libvirt-sock-ro' domstate beaker-test-vm1.beaker Without socket, I get the following error: *error: failed to connect to the hypervisor* *error: End of file while reading data: Ncat: No such file or directory.: Input/output error* This does not work for 'start' because I believe this is a read-only socket since I see the error: error: Failed to start domain beaker-test-vm1.beaker error: operation forbidden: read only access prevents virDomainCreate When I look at my laptop, there is no /var/run/libvirt/libvirt-sock. So.....I've been wondering whether RHEL7 virsh/libvirt is compatible with Fedora36. Is there a work-around? I can't change the distros on my laptop or VMs. Carol

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