June 2022 - Users - libvirt List Archives

Domain XML of a restored VM
by Tomáš Golembiovský 14 Jun '22

14 Jun '22

Hi, I am looking for clarification on what exactly is happening to the domain XML when resuming a suspended VM. We would like to make sure we don't lose any configuration and we also see some unexpected behavior. The VM with the name/UUID same as resumed VM may or may not already exist. If it does, what role does the original domain XML of a VM play when resuming? Is there any merging taking place between the existing domain XML and the domain XML stored in save image? Is the original XML simply thrown away and replaced? Is there any difference how the stored XML is treated compared to the XML passed in `virDomainRestoreFlags()`? I see some unexpected changes here. When I use `virDomainSaveImageGetXMLDesc()` to retrieve the stored XML and pass it unchanged to the `virDomainRestoreFlags()` the final domain XML is different then when `virDomainRestore()` is used or when `virDomainRestoreFlags()` with no `dxml` argument is used. We have: <graphics ... passwdValidTo='1970-01-01T00:00:01'> in the domain XML and the `passwdValidTo` argument disappears when domain XML is passed in `dxml` argument but it is preserved in other cases. Is this behavior expected? If yes, can we do anything to preserve the configuration? What other changes in domain XML can be expected? Thanks, Tomas -- Tomáš Golembiovský <tgolembi(a)redhat.com>

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vepa-mode directly attached interface
by Gionatan Danti 13 Jun '22

13 Jun '22

Hi all, I just realized that libvirt default for directly attached interface is vepa mode. I discovered it now because virt-manager automatically enables bridge mode, while cockpit-machines get the default vepa mode. This is unfortunate because, being vepa switches very rare, it means that using cockpit to configure directly attached interfaces causes guests to not talk each other. I have some questions: - can libvirt default be changed/configured somehow (ie: to automatically create bridge-mode directly attached interface when no mode is specified)? - how can I use virsh to discover machines with vepa-mode interfaces (virsh domiflist <domain> does not return the interface mode)? - can I change the interface type at runtime (virt-xml <domain> --edit --network type=direct,source.mode=bridge works for inactive domains only)? Thanks. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti(a)assyoma.it - info(a)assyoma.it GPG public key ID: FF5F32A8

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[Libvirt][emulator-cores][dpdk] Emulatorpin cpuset best practices
by Laurent Dumont 07 Jun '22

07 Jun '22

Hey folks, I am curious to understand a bit more the core use of the emulatorpin CPUs with libvirt. For example : <vcpupin vcpu='0' cpuset='34'/> <vcpupin vcpu='1' cpuset='14'/> <vcpupin vcpu='2' cpuset='10'/> <vcpupin vcpu='3' cpuset='30'/> <emulatorpin cpuset='10,14,30,34'/> In this case : - The VM has 4 vCPUs. - Each of the core is pinned to a physical/thread core - 34,14,10,30 - The emulatorpin is also attached to the same physical CPUs. In our case : - Same setup for cores. - Running DPDK inside the virtual machine. - The compute/libvirt is using OVS but without DPDK. What we saw is the following : - DPDK is polling two cores at 100% to process packets. - From the compute metrics, we see USER %usage at 100% when the application starts. - From the compute metrics, as traffic increases, we see %SYSTEM going up. - As %SYSTEM goes up, %USER goes down. We are not quite sure, but we are wondering if this could cause a direct impact to the ability of DPDK to process traffic at the same X speed? - We can "live" move the emulator CPU to other cores. - This seems to be the recommended default setup for VNF/NFV deployments. Feels like I am missing a piece of the puzzle but gotta start somewhere! Thanks!

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how to use "virsh shutdown domain --mode [initctl|signal|paravirt) ?
by Lentes, Bernd 01 Jun '22

01 Jun '22

Hi, ocasionally my Virtual Domains running on a pacmekaer cluster don't shutdown, although beeing told to do it. "virsh help shutdown" says: ... --mode <string> shutdown mode: acpi|agent|initctl|signal|paravirt How is it possible to use initctl or signal or paravirt ? What do i have to do ? What are the prerequisites ? Bernd -- Bernd Lentes System Administrator Institute for Metabolism and Cell Death (MCD) Building 25 - office 122 HelmholtzZentrum München bernd.lentes(a)helmholtz-muenchen.de phone: +49 89 3187 1241 fax: +49 89 3187 2294 http://www.helmholtz-muenchen.de/mcd Public key: 30 82 01 0a 02 82 01 01 00 b3 72 3e ce 2c 0a 6f 58 49 2c 92 23 c7 b9 c1 ff 6c 3a 53 be f7 9e e9 24 b7 49 fa 3c e8 de 28 85 2c d3 ed f7 70 03 3f 4d 82 fc cc 96 4f 18 27 1f df 25 b3 13 00 db 4b 1d ec 7f 1b cf f9 cd e8 5b 1f 11 b3 a7 48 f8 c8 37 ed 41 ff 18 9f d7 83 51 a9 bd 86 c2 32 b3 d6 2d 77 ff 32 83 92 67 9e ae ae 9c 99 ce 42 27 6f bf d8 c2 a1 54 fd 2b 6b 12 65 0e 8a 79 56 be 53 89 70 51 02 6a eb 76 b8 92 25 2d 88 aa 57 08 42 ef 57 fb fe 00 71 8e 90 ef b2 e3 22 f3 34 4f 7b f1 c4 b1 7c 2f 1d 6f bd c8 a6 a1 1f 25 f3 e4 4b 6a 23 d3 d2 fa 27 ae 97 80 a3 f0 5a c4 50 4a 45 e3 45 4d 82 9f 8b 87 90 d0 f9 92 2d a7 d2 67 53 e6 ae 1e 72 3e e9 e0 c9 d3 1c 23 e0 75 78 4a 45 60 94 f8 e3 03 0b 09 85 08 d0 6c f3 ff ce fa 50 25 d9 da 81 7b 2a dc 9e 28 8b 83 04 b4 0a 9f 37 b8 ac 58 f1 38 43 0e 72 af 02 03 01 00 01

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