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libvirt and Ledger Nano or hotswappable single USB port with virt-manager - almost there?
by Anonymous Aardvark 28 Jun '22

28 Jun '22

Hi I am holding off on a full VFIO system (with a host just used for hosting and main hardware forwarded) until after a build a new PC for the coming generation of graphics cards but I have started using virt-manager to partition my workspaces. My host is Ubuntu 20.04 running QEMU v 5.0 on and Intel i5-4690K CPU and GA-Z97X-Gaming 5 motherboard. Guest is Debian 11. I am trying to solve the issue of how the Ledger Nano X changes its product ID when using different applications <https://imil.net/blog/posts/2020/ledger_on_kvm/>. Unfortunately all ports seem to be in the same IOMMU group so I cannot just forward a controller. I have learned that although my temporary fallback Virtualbox allows forwarding by vendor ID without a product ID <https://www.reddit.com/r/ledgerwallet/comments/mf872x/how_can_you_run_ledge…>, and I have seen some libvirt references to this, including mention of a patch that apparently should have been implemented I have not been able to make it work: from QEMU to libvirt(virsh) - add USB-port <https://stackoverflow.com/questions/46421962/from-qemu-to-libvirtvirsh-add-…> Can I pass through a USB Port via qemu Command Line? <https://unix.stackexchange.com/questions/452934/can-i-pass-through-a-usb-po…> Detail on on my comprehensive hotplugger attempts to forward a single port here <https://www.reddit.com/r/VFIO/comments/lbvgpr/comment/idzml1k/?utm_source=s…> . Can you please tell me if there is some way I can edit either my debian.xml or how hotplugger interacts with the socket so that I can forward a single port that is hotswapable and/or so that Ledger Nano X will stay visible on the guest even after it changes product ID? Thanks Aard.

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Domain XML and VLAN tagging
by Gionatan Danti 19 Jun '22

19 Jun '22

Hi all, from here [1]: "Network connections that support guest-transparent VLAN tagging include 1) type='bridge' interfaces connected to an Open vSwitch bridge Since 0.10.0 , 2) SRIOV Virtual Functions (VF) used via type='hostdev' (direct device assignment) Since 0.10.0 , and 3) SRIOV VFs used via type='direct' with mode='passthrough' (macvtap "passthru" mode) Since 1.3.5 . All other connection types, including standard linux bridges and libvirt's own virtual networks, do not support it." I read it correctly that when used on a classical linux bridge these vlan tags does nothing? If so, it is due to something related to the underlying bridge device (ie: incomplete support for vlan filtering) or it is because libvirt lacks the necessary "plumbing" to use advanced bridge features? Thanks. [1] https://libvirt.org/formatdomain.html#setting-vlan-tag-on-supported-network… -- 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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managed save returns "migration with virtiofs device is not supported"
by Francesc Guasch 16 Jun '22

16 Jun '22

Hello. I have a virtual machine with a virtiofs entry configured. When I try to do a managed save it fails with this message: libvirt error code: 55, message: Requested operation is not valid: migration with virtiofs device is not supported This is libvirt 8.0.0 that comes with Ubuntu 22.04. I have seen the current release in git is libvirt 8.5 . I will try to build from source and try again if you think this was not the expected behaviour. This is the filesystem entry: <filesystem type='mount' accessmode='passthrough'> <driver type='virtiofs'/> <source dir='/home/shared'/> <target dir='home_shared'/> <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/> </filesystem> Sorry if this is not the right place to ask. I can write an issue in gitlab or whatever is more appropriate. Thanks !

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managed save returns "migration with virtiofs device is not supported"
by Francesc Guasch 15 Jun '22

15 Jun '22

Hello. I have a virtual machine with a virtiofs entry configured. When I try to do a managed save it fails with this message: libvirt error code: 55, message: Requested operation is not valid: migration with virtiofs device is not supported This is libvirt 8.0.0 that comes with Ubuntu 22.04. I have seen the current release in git is libvirt 8.5 . I will try to build from source and try again if you think this was not the expected behaviour. This is the filesystem entry: <filesystem type='mount' accessmode='passthrough'> <driver type='virtiofs'/> <source dir='/home/shared'/> <target dir='home_shared'/> <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/> </filesystem> Sorry if this is not the right place to ask. I can write an issue in gitlab or whatever is more appropriate. Thanks !

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After restarted libvirtd service, live migration VM hit an issue 'Target CPU check default does not match source none'
by 梁朝军 15 Jun '22

15 Jun '22

Hi All, After restarted the libvirtd service on the source host, we start live migration VM to destination host and often hit an issue 'unsupported configuration: Target CPU check default does not match source none’ We don’t configure any special setting for CPU model when start VM and I think it should be ‘custom’ mode by default . Furthermore , those two hosts for doing live migration have almost the same capabilities as below. It’s confused me why failed to check the cpu configuration after restart libvitd service on source host? The libvirt version is 7.9.0, package: 1.el8 (Unknown, 2021-11-28-22:35:11) private build Host OS version : rhat8.4 QEMU version: QEMU 5.1 private build Any comments are appreciated. Thanks

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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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Virtiofs xattr options on domain xml
by ksobrenat32 23 May '22

23 May '22

Hi! I have a debian 11 (bullseye) machine running libvirtd version 7.0.0 and a RHEL 9 virtual machine that I need to share a disk and though about virtiofs. The disk is a btrfs disk and I have successfully mount it with: <filesystem type='mount' accessmode='passthrough'> <driver type='virtiofs' queue='1024'/> <binary path='/usr/lib/qemu/virtiofsd' xattr='on'> <cache mode='always'/> <lock posix='on' flock='on'/> </binary> <source dir='/mnt/WD-Disk'/> <target dir='media'/> <alias name='fs0'/> <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/> </filesystem> The problem I have is with selinux, when I try to change the context of a file inside the virtual machine I get a 'Operation not permitted' error, I can change the context in the Debian host and see the changes in the virtual machine but I would want to be able to change the context from the vm to able to use podman containers with selinux enabled. I see on the docs https://qemu.readthedocs.io/en/latest/tools/virtiofsd.html#selinux-support you can run virtiofsd with a xattr option so it is compatible with selinux but I do not find a way to change the domain xml to add this option, is there a way to add this option? Does a better option exists (maybe on the guest side)?

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