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

01 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?

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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

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systemtap stapvirt tool
by Stan Cox 07 Jul '22

07 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

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Storage Pool - NFS v4.1
by Charles Koprowski 01 Jul '22

01 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.

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