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Can RHEL7 VM run remote commands to Fedora36 host?
by Carol Bouchard 02 Aug '22

02 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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Can RHEL7 VM run remote libvirt commands to Fedora36 host?
by Carol Bouchard 02 Aug '22

02 Aug '22

I have a test environment that use to work but no longer does. My laptop is Fedora36 (libvirt version 8.1.0.2) while the VMs it spawns are RHEL7 (max libvirt version is 4.5.0). The source of my problem seems to be that RHEL7 libvirt needs rw socket /var/run/libvirt/libvirt-sock which no longer exists in fedora36. The following is successful from RHEL7 VM to laptop: virsh -d0 --connect 'qemu+ssh://192.168.120.1/system?*socket*=/var/run/libvirt/libvirt-sock-ro' domstate beaker-test-vm1.beaker If I change the action from domstate to start, it fails on error: Failed to start domain beaker-test-vm1.beaker error: operation forbidden: read only access prevents virDomainCreate which made me realize ro stands for read-only; however, there is no libvirt-sock. I tried some of the other socket files without success. Is there a work-around? Carol

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how to get vm uptime through libvirt api
by Jiatong Shen 26 Jul '22

26 Jul '22

Hello community, I would like to know if there is an api to get a virtual machine's uptime. Thank you in advance for the help. -- Best Regards, Jiatong Shen

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Eject CD ROM medium fails with 'Tray of device is not open'
by liang chaojun 25 Jul '22

25 Jul '22

Hi Guys, I have hit an issue on testing against our testbed, It's failed to eject cdrom media after reboot from installed the guest OS. The reproduce step: 1. Attach a block device with a ISO media and start install VM from ISO. 2. <disk type='block' device='cdrom'> <driver name='qemu' type='raw'/> <source dev='/dev/disk/by-id/pbdx-vol-cfe60dca-c271-491b-be3c-11fa8d7625a4' index='6'/> <backingStore/> <target dev='hda' bus='ide' tray='open'/> <readonly/> <alias name='ide0-0-0'/> <address type='drive' controller='0' bus='0' target='0' unit='0'/> </disk> 3. After installed the OS and reboot from system disk successful. 4. Then I want to eject CDROM through update device with the xml like below or using virsh tool 'virsh change-media iso_test hda --eject' 5. All those will failed at "internal error: unable to execute QEMU command 'blockdev-remove-medium': Tray of device 'ide0-0-0' is not open" <disk type='block' device='cdrom'> <driver name='qemu' type='raw'/> <backingStore/> <target dev='hda' bus='ide' tray='open'/> <readonly/> <alias name='ide0-0-0'/> <address type='drive' controller='0' bus='0' target='0' unit='0'/> </disk> block info looks like below: virsh qemu-monitor-command iso_test --hmp info block setlocale: No such file or directory libvirt-6-format: /dev/disk/by-id/pbdx-vol-cfe60dca-c271-491b-be3c-11fa8d7625a4 (raw, read-only) Attached to: ide0-0-0 Removable device: locked, tray closed Cache mode: writeback Reproduce envrionment: Operating system: rhat8.4 Architecture:x86 kernel version:4.18.0-305 libvirt version:v7.9.0(private build) Hypervisor and version:QEMU 5.1.0(private build) Is there any workaround? Any comments are appreciated. Thanks!

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NetworkD or NetworkManager. Does it matter?
by Mnecraftchest1 24 Jul '22

24 Jul '22

Hello there. I am in the process of building an Arch Linux install for a virtualization server for my home lab, and I am trying to decide what networking system I should use. The two I am considering are SystemD-NetworkD, and NetworkManager. Looking along the lines of support from libvirt, would I be better off with one or the other, or does it not matter which one I use?

1 0

The default USB controller of pc machine type
by Han Han 15 Jul '22

15 Jul '22

Hello, I found that the default USB controller for q35 machine type is qemu-xhci while for pc it is piix3-uhci. Here are the results(on qemu-kvm-7.0.0 qemu-kvm-7.0.0): ➜ ~ cat /tmp/usb.xml <domain type="kvm"> <name>USB</name> <uuid>1a81d4ef-6537-4ae8-b257-8a15e0c0525f</uuid> <memory>2097152</memory> <currentMemory>2097152</currentMemory> <vcpu>1</vcpu> <os> <type arch="x86_64" machine="q35">hvm</type> <boot dev="hd"/> </os> <devices> <emulator>/usr/libexec/qemu-kvm</emulator> </devices> </domain> ➜ ~ virsh define /tmp/usb.xml && virsh dumpxml USB|grep usb Domain 'USB' defined from /tmp/usb.xml <controller type='usb' index='0' model='qemu-xhci'> ➜ ~ cat /tmp/usb-pc.xml <domain type="kvm"> <name>USB</name> <uuid>1a81d4ef-6537-4ae8-b257-8a15e0c0525f</uuid> <memory>2097152</memory> <currentMemory>2097152</currentMemory> <vcpu>1</vcpu> <os> <type arch="x86_64" machine="pc">hvm</type> <boot dev="hd"/> </os> <devices> <emulator>/usr/libexec/qemu-kvm</emulator> </devices> </domain> ➜ ~ virsh define /tmp/usb-pc.xml && virsh dumpxml USB|grep usb Domain 'USB' defined from /tmp/usb-pc.xml <controller type='usb' index='0' model='piix3-uhci'> And the default usb controller for q35 has been added since: ed2049ea19 qemu: auto-add generic xhci rather than NEC xhci to Q35 domains As I know, pc machine supports qemu-xhci as well. Morever, the performance of qemu-xhci is better than piix3-uhci. So why not update the default usb controller of pc machine type to qemu-xhci? I think we can improve it here.

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Why can not get the expected cpu topology after setting the maxcpu in xml?
by liang chaojun 15 Jul '22

15 Jul '22

Hello all, I hit a issue that I'm not able to see the expected cpu topology in VM after setting the maxcpu arrtribute in domain. the xml look like below: <vcpu placement='static' current='4'>8</vcpu> <cpu mode='host-passthrough' check='none' migratable='on'> <topology sockets='2' dies='1' cores='4' threads='1'/> </cpu> I notice that the cpu topoloy looked like below capture output from 'lscpu' tool which is totally different with my setting. CPU(s): 4 On-line CPU(s) list: 0-3 Thread(s) per core: 1 Core(s) per socket: 4 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 63 Model name: Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz Besides i found it looked correct if i relpace 'vcpu' line with "<vcpu placement='static'>8</vcpu>" that remove maxcpu value. Could you give me some information? Any comments are appreciated. Thanks

1 0

systemtap stapvirt tool
by Stan Cox 08 Jul '22

08 Jul '22

I am having a quandary with libvirt and am wondering if someone can shed some light. Systemtap converts a probing and instrumentation language into a kernel module. The module can optionally be run remotely via ssh or libvirt. The libvirt mechanism is not working (not yet sure of timing of regression) The systemtap stap command pipes to a stapvirt command that is the libvirt interface. The remote is running a stapsh tool that receives the requests. The initial commands are sent and received okay (strace output on remote) but never receives the stap kernel module: # local sent option data request [pid 11959] read(3, "option data\n", 4096) = 12 # remote says OK [pid 11959] write(3, "OK\n", 3) = 3 [pid 11959] poll([{fd=3, events=POLLIN}, {fd=0, events=0}, {fd=0, events=0}], 3, -1) = 1 ([{fd=3, revents=POLLIN}]) [pid 11959] --- SIGIO {si_signo=SIGIO, si_code=SI_KERNEL} --- [pid 11959] poll([{fd=3, events=POLLHUP}], 1, 0) = 0 (Timeout) [pid 11959] rt_sigreturn({mask=[]}) = 1 # local sent file ... request to download the module [pid 11959] read(3, "file 926928 stap_1f18b4b54e74602"..., 4096) = 58 # remote opens the module [pid 11959] openat(AT_FDCWD, "stap_1f18b4b54e74602a0a1f0685f2f7333e_1006.ko", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 4 # but never receives it [pid 11959] read(3, "", 4096) = 0 The local sets up callbacks for stdin, stdout, stream: ctxt.stdin_w = virEventAddHandle(STDIN_FILENO, VIR_EVENT_HANDLE_READABLE, stdin_event, &ctxt, NULL); ... ctxt.stdout_w = virEventAddHandle(STDOUT_FILENO, 0, stdout_event, &ctxt, NULL); ... virStreamEventAddCallback(ctxt.st, VIR_STREAM_EVENT_READABLE | VIR_EVENT_HANDLE_WRITABLE, stream_event, &ctxt, NULL) < 0) Then starts an even loop while (!disconnect) { if (virEventRunDefaultImpl() != 0) break; } stream_event is notified for the command requests, but is not notified for the kernel module chunks: stdin_event excerpt: bytes_read = read(fd, ctxt->termbuf + ctxt->termbuf_off, sizeof(ctxt->termbuf) - ctxt->termbuf_off); ... ctxt->termbuf_off += bytes_read; ... if (ctxt->termbuf_off) { // we have stuff to write to the stream virStreamEventUpdateCallback(ctxt->st, VIR_STREAM_EVENT_READABLE | VIR_STREAM_EVENT_WRITABLE); } stream_event excerpt: if ((events & VIR_STREAM_EVENT_READABLE) && (ctxt->stbuf_off < sizeof(ctxt->stbuf))) { int bytes_recv = virStreamRecv(st, ctxt->stbuf + ctxt->stbuf_off, sizeof(ctxt->stbuf) - ctxt->stbuf_off); I notice https://libvirt.org/html/libvirt-libvirt-stream.html has an example using virStreamSend. Is that the preferred way to do the above?

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Incomplete information in the website Wiki for libvirt.org
by Uriel Emmanuel Pelaez Hernández 04 Jul '22

04 Jul '22

Dear Web Marster from wiki.libvirt.org, I tried to look for the libvirtd, the demon that is suppose to run under Linux/Unix environment, but your site didn't show any information. Only a statement appeared: "Create the page libvirtd " Please, update your site or suggest any other weblink with the information. In theory CygWin use your package, but the information is incomplete too, about this issue. I send this mail to these both Email address by the information displayed in your wiki, about the contact address to solve this kind of problems. By now, Google Service in my region is deprecated, so the information that the WebBrowser display is not the best. I send this request from my Email of Graduated Student form the University domain. Best Regards, Mr. Peláez Uriel. Mexico City

2 1

Storage Pool - NFS v4.1
by Charles Koprowski 02 Jul '22

02 Jul '22

Hello, In order to use pNFS which is only available in NFS version 4.1, I'm trying to create a netfs storage pool specifying the protocol version to be used : <pool type="netfs"> <name>vms</name> <source> ... <format type="nfs"/> <protocol ver='4.1'/> </source> <target> ... </pool> But the storage pool XML documentation [1] states that : protocol For a netfs Storage Pool provide a mechanism to define which NFS protocol version number will be used to contact the server's NFS service. The attribute ver accepts an unsigned *integer* as the version number to use. And indeed, when I try to virsh pool-define I get : error: Failed to define pool from pool.xml error: XML error: storage pool protocol ver '4.1' is malformed How can I specify the desired NFS minor version to libvirt ? I could mount the NFS share myself and build a dir storage pool on top of it but that's not very pretty. Thank you, [1] https://libvirt.org/formatstorage.html -- Charles

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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.

1 0

Domain XML and VLAN tagging
by Gionatan Danti 20 Jun '22

20 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 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 !

1 0

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 14 Jun '22

14 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 24 May '22

24 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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something (qemu?) is leaking
by lejeczek 23 May '22

23 May '22

Hi guys. I do a simple thing which should be easy to reproduce. -> $ virt-install -n rum1 --virt-type kvm --os-variant centos8 --memory $((4*1024)) --disk=/VMs3/rum1.qcow2,device=disk,bus=virtio --network network=10_3_1,model=virtio --graphics=listen=0.0.0.0 --cpu EPYC-Rome --vcpus 3 --cdrom /VMs3/CentOS-Stream-9-latest-x86_64-dvd1.iso During manual setup in the VM I set 'hostname' to something and when installation begins and disk config stage takes place I can see - and later when VM(c9s) is ready can confirm - that VG name is taken from another VM defined/running on the host. Host is c9s with: qemu-kvm-7.0.0-1.el9.x86_64 libvirt-daemon-8.2.0-1.el9.x86_64 5.14.0-86.el9.x86_64 Does anybody see this/similar? many thanks, L.

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Slow VM start/revert, when trying to start/revert dozens of VMs in parallel
by Petr Beneš 20 May '22

20 May '22

Hi, my problem can be described simply: libvirt can't handle starting dozens of VMs at the same time. (technically, it can, but it's really slow.) We have an AMD machine with 256 logical cores and 1.5T ram. On that machine there is roughly 200 VMs. Each VM is the same: 8GB of RAM, 4 VCPUs. Half of them is Win7 x86, the other half is Win7 x64. VMs are using qcow2 as the disk image. These images reside in the ramdisk (tmpfs). We use these machines for automatic malware analysis, so our scenario consists of this cycle: - reverting VM to a running state - execute sample inside of the VM for ~1-2 minutes - shutdown the VM Of course, this results in multiple VMs trying to start at the same time. At first, reverts/starts are really fast - second or two. After about a minute, the "revertToSnapshot" suddenly takes 10-15 seconds, which is really unacceptable. For comparison, we're running the same scenarion on Proxmox, where the revertToSnapshot usually takes 2 seconds. Few notes: - Because of this fast cycle (~2-3 minutes) and because of VMs taking 10-15 seconds to start, there is barely more than 25-30 VMs running at once. We would really love to utilise the whole potential of such beast machine of ours, and have at least ~100 VMs running at any given time. - During the time running, the avg. CPU load isn't higher than 25%. Also, there's only about 280 GB of RAM used. Therefore, it's not limitation of our resources. - When the framwork is running and libvirt is making its best to start our VMs, I noticed that every libvirt operation is suddenly very slow. Even simple "virsh list [--all]" takes few seconds to complete, even though it finishes instantly when no VM is running/starting. I was trying to search for this issue, but didn't really find anything besides this presentation: https://events19.linuxfoundation.org/wp-content/uploads/2017/12/Scalability… However, I couldn't find those commits in your upstream. Is this a known issue? Or is there some setting I don't know of which would magically make the VMs start faster? As for steps to reproduce - I don't think there is anything special needed. Just try to start/destroy several VMs in a loop. There is even provided one-liner for that in the presentation above. ``` # For multiple domains: # while virsh start $vm && virsh destroy $vm; do : ; done # → ~30s hang ups of the libvirtd main loop ``` Best Regards, Petr

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macvtap with disconnected physical interface
by Gionatan Danti 20 May '22

20 May '22

Dear list, I just discovered the hard way that if the lower lever physical interface of a macvlan bridge is disconnected (ie: by unplugging the eth cable, resulting in no carrier), inter-guest network traffic from all virtual machines bound to the disconnected interface is dropped. This behavior surprises me, as with the classic bridges I can disconnect the underlying physical interface without causing any harm to inter-guest traffic. Am I doing something wrong, or this really is the expected behavior? If so, can I force the macvtap interfaces to bridge traffic even when the underlying physical interface is disconnected? Regards. -- 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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Updating domains definitions via API
by Darragh Bailey 17 May '22

17 May '22

Hi, Looking into a bug in vagrant-libvirt where an error during the update will cause the domain to be completely discarded. https://github.com/vagrant-libvirt/vagrant-libvirt/issues/949 Basically I think it stems from doing an undefine -> create with XML new process, which if there is an issue with the new XML due to KVM module not loaded or something similar it will be rejected, but unfortunately it is also unlikely to allow the old definition to be restored either. I'm looking around to try and see if there is an API (specfically in ruby-libvirt) for updating the domain definition, so that if the new XML is rejected at least the old definition remains, and so far I'm drawing a blank. Is the only option here to write using a temporary domain name, then remove the old domain and rename the new definition to the old domain? Or have I missed the obvious API analogous to the edit functionality? -- Darragh Bailey "Nothing is foolproof to a sufficiently talented fool" - unknown

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Problem calling 'virsh' in a script
by Digimer 16 May '22

16 May '22

3 4