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Does Libvirt's json parser support single quoted string in qmp json string?
by Peter Luo 05 Feb '20

05 Feb '20

Hi All, I’m using qmp command via “virsh qemu-monitor-command” to perform block related jobs. And in my case, I execute block-commit to commit the changes in the top image to the base image which is encrypted. So in the base parameter, I need a json string which is single quoted to support the encryption parameters. However, the virsh is failed to parse the whole json qmp command. Attempt 1: Single quote without backflash, failed root@host:~# virsh qemu-monitor-command i-9wdfw2x8 "{\"execute\": \"block-commit\", \"arguments\": { \"device\": \"drive-virtio-disk2\", \"job-id\": \"job100\", \"base\":'json:{\"encrypt.key-secret\":\"vol-38973xjl.secret\",\"driver\":\"qcow2\",\"file\":{\"driver\":\"file\",\"filename\":\"/pitrix/data/container/vol-38973xjl.img\"}}', \"top\": \"/pitrix/data/container/vol-38973xjl_ss-2tw7v0mm.img\"}}" error: internal error: cannot parse json {"execute": "block-commit", "arguments": { "device": "drive-virtio-disk2", "job-id": "job100", "base":'json:{"encrypt.key-secret":"vol-38973xjl.secret","driver":"qcow2","file":{"driver":"file","filename":"/pitrix/data/container/vol-38973xjl.img"}}', "top": "/pitrix/data/container/vol-38973xjl_ss-2tw7v0mm.img"}}: lexical error: invalid char in json text. , "job-id": "job100", "base":'json:{"encrypt.key-secret":"vo (right here) ------^ Attempt 2: Single quote with backflash, failed root@host:~# virsh qemu-monitor-command i-9wdfw2x8 "{\"execute\": \"block-commit\", \"arguments\": { \"device\": \"drive-virtio-disk2\", \"job-id\": \"job100\", \"base\":\'json:{\"encrypt.key-secret\":\"vol-38973xjl.secret\",\"driver\":\"qcow2\",\"file\":{\"driver\":\"file\",\"filename\":\"/pitrix/data/container/vol-38973xjl.img\"}}\', \"top\": \"/pitrix/data/container/vol-38973xjl_ss-2tw7v0mm.img\"}}" error: internal error: cannot parse json {"execute": "block-commit", "arguments": { "device": "drive-virtio-disk2", "job-id": "job100", "base":\'json:{"encrypt.key-secret":"vol-38973xjl.secret","driver":"qcow2","file":{"driver":"file","filename":"/pitrix/data/container/vol-38973xjl.img"}}\', "top": "/pitrix/data/container/vol-38973xjl_ss-2tw7v0mm.img"}}: lexical error: invalid char in json text. , "job-id": "job100", "base":\'json:{"encrypt.key-secret":"v (right here) ------^ My libvirt version is 5.7.0, libyajl is 2.1.0. Thanks, Peter Luo

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USB devices with same vendor:product id
by Maxime Accadia 03 Feb '20

03 Feb '20

Hi, We have a VM with several USB devices attached. Everything works well, but sometimes, after a reboot of the host, some usb device get a different bus/device number and that prevent the reboot of the VM : ------- error: Failed to start domain xxx error: internal error: Did not find USB device 04b9:0300 bus:1 device:5 ------- I guess this is because we have multiple usb devices with the same vendor/product ID : ------- <hostdev mode='subsystem' type='usb' managed='yes'> <source> <vendor id='0x04b9'/> <product id='0x0300'/> <address bus='2' device='4'/> </source> <alias name='hostdev0'/> <address type='usb' bus='0' port='2'/> </hostdev> <hostdev mode='subsystem' type='usb' managed='yes'> <source> <vendor id='0x0529'/> <product id='0x0001'/> <address bus='1' device='7'/> </source> <alias name='hostdev1'/> <address type='usb' bus='0' port='1.2'/> </hostdev> <hostdev mode='subsystem' type='usb' managed='yes'> <source> <vendor id='0x0529'/> <product id='0x0001'/> <address bus='2' device='3'/> </source> <alias name='hostdev2'/> <address type='usb' bus='0' port='1.4'/> </hostdev> <hostdev mode='subsystem' type='usb' managed='yes'> <source> <vendor id='0x04b9'/> <product id='0x0300'/> <address bus='1' device='6'/> </source> <alias name='hostdev3'/> <address type='usb' bus='0' port='1.1'/> </hostdev> ------- Any idea on how to handle this case ? We were thinking about using udev, but it seems that libvirt only supports vendor/id (not unique in our case) and bus/device (not predictable) to identify usb devices. Thanks, Maxime Accadia P.S. We use libvirt 4.0.0 on Ubuntu 18.04

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Re: Does Libvirt's json parser support single quoted string in qmp json string?
by Peter Luo 31 Jan '20

31 Jan '20

Hi Peter Krempa, Thanks for your quick response, yes, I know since libvirt 5.8, the -blockdev is used for disk by default. However we have to maintain the old releases for the production environment for a while, so I still need use the old way to create the disk. >"base" argument must be a string. this means you need double quotes in >JSON ("). You also must properly escape any further JSON. > Do you mean the base argument need be formatted like below? \"base\":\"json:{\"encrypt.key-secret\":\"vol-38973xjl.secret\",\"driver\":\"qcow2\",\"file\":{\"driver\":\"file\",\"filename\":\"/pitrix/data/container/vol-38973xjl.img\"}}\" Please help me to point out where the examples are located? I did take a quick look at those test files, but no one seems to be matched with my case. Thanks, Peter Luo On 31/1/20, 6:52 PM, "Peter Krempa" <pkrempa(a)redhat.com> wrote: On Fri, Jan 31, 2020 at 18:38:33 +0800, Peter Luo wrote: > Hi All, > > > > I’m using qmp command via “virsh qemu-monitor-command” to perform block related jobs. > > And in my case, I execute block-commit to commit the changes in the top image to the base image which is encrypted. > > So in the base parameter, I need a json string which is single quoted to support the encryption parameters. > > However, the virsh is failed to parse the whole json qmp command. None of the above should be required with libvirt-5.10 and later when using qemu-4.2. Those two versions start using blockdev way of specifying images and encrypted images are supported. Please consider using libvirt-6.0 though as there are few fixes for blockdev. > > > > Attempt 1: Single quote without backflash, failed > > root@host:~# virsh qemu-monitor-command i-9wdfw2x8 "{\"execute\": \"block-commit\", \"arguments\": { \"device\": \"drive-virtio-disk2\", \"job-id\": \"job100\", \"base\":'json:{\"encrypt.key-secret\":\"vol-38973xjl.secret\",\"driver\":\"qcow2\",\"file\":{\"driver\":\"file\",\"filename\":\"/pitrix/data/container/vol-38973xjl.img\"}}', \"top\": \"/pitrix/data/container/vol-38973xjl_ss-2tw7v0mm.img\"}}" > > error: internal error: cannot parse json {"execute": "block-commit", "arguments": { "device": "drive-virtio-disk2", "job-id": "job100", "base":'json:{"encrypt.key-secret":"vol-38973xjl.secret","driver":"qcow2","file":{"driver":"file","filename":"/pitrix/data/container/vol-38973xjl.img"}}', "top": "/pitrix/data/container/vol-38973xjl_ss-2tw7v0mm.img"}}: lexical error: invalid char in json text. > > , "job-id": "job100", "base":'json:{"encrypt.key-secret":"vo "base" argument must be a string. this means you need double quotes in JSON ("). You also must properly escape any further JSON. Given that libvirt now supports the operation natively I'll refrain from elaborating on how to properly escape JSON to contain JSON strings, but there are few examples in the test suite. But please use the upstream supported way instead.

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Detecting of features of VMs
by Peter Krempa 29 Jan '20

29 Jan '20

Hi, I was asked by Nir and Eyal of the oVirt project on how to detect whether a certain feature is supported by libvirt. As I thought it might be better to document this publically rather than being lost in a private thread I'm posting this to libvirt-users. The specific question will be answered below. --- There are currently two interfaces which allow discovery of libvirts and in turn qemu's capabilities. Both return an XML which describes various aspects of the hosts or VMs capabilities. virConnectGetCapabilities(conn) https://libvirt.org/formatcaps.html The XML returned by this API describes mostly the host itself, the CPU, NUMA topology, security driver support, migration features but also describes guests architectures supported by the guest. In case of the qemu driver the guest section describes some of the aspects and configurations supported by the default qemu binary, the machine types and virtualization types it supports. Additionally the <features> section describes support for some long-existing features such as ACPI, APIC and disk snapshots. As these features are supported for a long time, it can be assumed that they are present (at least in case of the qemu driver) when the second API is present. Now while the virConnectGetCapabilities API provides mostly useful information about the host, the limitation of not being able to report information about specific qemu binaries or machine types lead to introduction. virConnectGetDomainCapabilities(conn, emulator_binary_path, architecture, machine_type, virt_type, flags) https://libvirt.org/formatdomaincaps.html The XML returned by this API describes the capabilities of an VM which would be started using the parameters given to the API (note that if the parameters are NULL a default is provided). The <os> subelement describes supported OS loader types and firmware binaries. <cpu> describes which CPU models are supported by the emulator and also the CPU which would be used if 'host-model' is selected as the CPU model. The <devices> section describes models and some properties of devices supported by the VM. The 'enum's reported in this XML map to supported values of some of the fields we report the possible configurations for. Note that these values are reported individually and all combinations aren't necessarily supported. The last section 'features' describes whether some high-level features supported by such a VM. The features themselves are described in the documentation above. Note that the entries into 'features' are added arbitrarily depending on whether a feature is deemed important enough to be exposed. So please feel free to report if anything is missing or it would be helpful if we reported any feature. --- Now specifically to the question: I was asked on when it's safe to pass VIR_DOMAIN_UNDEFINE_CHECKPOINTS_METADATA to virDomainUndefine. In this case it's safe to pass it if <features> contains the <backup> element regardless of the value of 'supported' attribute. I'll also mention this in the documentation of the domain caps XML.

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Host CPU usage high on guest network load (macvtap).
by André Malm 28 Jan '20

28 Jan '20

Hello, Is it reasonable for one CPU on the host to be loaded 20-30% on 100 mbps download in a guest? There is barely any (1-2%) load in the guest. The host is running ubuntu 18.04 on an Intel i7-7700K, virtualization etc is enabled. Everything except host load on guest network activity is fine. This is how i setup the network with virt-install: --network type=direct,source=enp1s0,source_mode=bridge,model=virtio,mac=00:11:22:33:44:55 In the guest (ubuntu18.04 cloud minimal) i run a simple wget, setting mode to vepa still works but the cpu load is the same.

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Emulation packages for Centos8
by Mauricio Tavares 28 Jan '20

28 Jan '20

So I was looking for the qemu-system-ppc so I could emulate that cpu in my Intel I7 centos8 box. So far I found that available for fedora (and ubuntu) but not centos. Does anyone have a suggestion for where (repo) I can get said package?

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NFS and unsafe migration
by Gionatan Danti 28 Jan '20

28 Jan '20

Hi all, I have a question about NFS datastore and unsafe migration. When migrating a virtual machine having a virtio disk in writeback cache between two hosts sharing a single NFS datastore, I get the following error: "Unsafe migration: Migration may lead to data corruption if disks use cache != none or cache != directsync" I understand why libvirt alerts for unsafe migration in cases where no coherency is enfoced by the underlying system; however, is it really the case for nfs? From what I know (and from the man page), by default nfs has open-to-close consistency, which seems quite right for migrating a virtual machine between (as only one host at a time reads/writes/locks the virtual disk files). I know that I can simply use cache=none to let the problem go away; however, this significantly impairs performance when used on nfs. Am I missing something? 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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KVM not available on system bus
by Kasper Laudrup 28 Jan '20

28 Jan '20

Hi libvirt-users, Hope this is the right place to ask, otherwise please point me in the right direction. I have a libvirt virtual machine running on the session bus that I would like to access through SSH. I have previously done so using X11 forwarding and while it works, it is very sluggish with the connection I have. I recently learned that you can access the virtual machine with virt-viewer through SSH which should perform much better. Unfortunately, my virtual machine is currently running on the session bus and that doesn't seem to be supported (please do correct if I'm wrong here). It doesn't really matter to much if the VM is running on the system bus or session bus, I just prefer running things as a non privileged user for all the obvious reasons, so that's where I created the VM initially. I tried to follow this guide to move my VM to the system bus. Running `sudo virsh define vm.xml` fails with: error: invalid argument: could not find capabilities for arch=x86_64 domaintype=kvm Digging a bit further into it, I figured out that the cause of the error message is, that I for some reason do not have KVM acceleration support when running VMs on the system bus (as root) running my VM on the session bus as a normal user (with the correct group membership) works fine. Trying to launch virt-manager as root verifies that, as creating a new VM warns me that I do not have KVM support. I'm fairly lost as to what to do from here. I must admit I remember struggling a bit to get the virtual machine to run with KVM support on the session bus in the first place, but have completely forgotten what the problem and resolution was. I'm using Debian stable (Buster) with standard package versions: QEMU 3.1.0 libvirt 5.0.0 Any kind of help or input would be greatly appreciated. Thanks a lot and kind regards, Kasper Laudrup

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VM crash, partitiontable deleted CPU 1/KVM[2867866]: segfault at 2 ip 0000560cffe03757 sp 00007f0e8babaeb0 error 4 in qemu-system-x86_64
by Oliver Dzombic 27 Jan '20

27 Jan '20

Hi, Got from a running machine suddenly: [859069.022739] CPU 1/KVM[2867866]: segfault at 2 ip 0000560cffe03757 sp 00007f0e8babaeb0 error 4 in qemu-system-x86_64[560cffbd4000+45d000] [859069.022749] Code: 00 00 00 41 57 41 56 41 55 41 54 49 89 cc b9 a2 03 00 00 55 48 89 f5 48 8d 35 1c 35 29 00 53 48 89 fb 48 83 c7 38 48 83 ec 38 <44> 0f b7 52 02 4c 8b 7a 08 4c 89 44 24 08 4c 8d 05 b4 08 29 00 45 [859087.661975] device k1806-YcXLF left promiscuous mode # qemu-system-x86_64 --version QEMU emulator version 4.2.0 (qemu-4.2.0-2.fc31) Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers # virsh -V Virsh command line tool of libvirt 6.0.0 See web site at https://libvirt.org/ Compiled with support for: Hypervisors: QEMU/KVM LXC LibXL OpenVZ VMware VirtualBox ESX Hyper-V Test Networking: Remote Network Bridging Interface netcf Nwfilter VirtualPort Storage: Dir Disk Filesystem SCSI Multipath iSCSI LVM RBD Sheepdog Gluster ZFS Miscellaneous: Daemon Nodedev SELinux Secrets Debug DTrace Readline After that the partition table of the zfs volume was cleared. I also opened a bug report with all informations i could get so far: https://bugzilla.redhat.com/show_bug.cgi?id=1795082 I am thankful for any idea / suggestion. Thank you -- Mit freundlichen Gruessen / Best regards Oliver Dzombic Layer7 Networks mailto:info@layer7.net Anschrift: Layer7 Networks GmbH Zum Sonnenberg 1-3 63571 Gelnhausen HRB 96293 beim Amtsgericht Hanau Geschäftsführung: Oliver Dzombic UST ID: DE259845632

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VM crash, partitiontable deleted CPU 1/KVM[2867866]: segfault at 2 ip 0000560cffe03757 sp 00007f0e8babaeb0 error 4 in qemu-system-x86_64
by Oliver Dzombic 27 Jan '20

27 Jan '20

Hi, Got from a running machine suddenly: [859069.022739] CPU 1/KVM[2867866]: segfault at 2 ip 0000560cffe03757 sp 00007f0e8babaeb0 error 4 in qemu-system-x86_64[560cffbd4000+45d000] [859069.022749] Code: 00 00 00 41 57 41 56 41 55 41 54 49 89 cc b9 a2 03 00 00 55 48 89 f5 48 8d 35 1c 35 29 00 53 48 89 fb 48 83 c7 38 48 83 ec 38 <44> 0f b7 52 02 4c 8b 7a 08 4c 89 44 24 08 4c 8d 05 b4 08 29 00 45 [859087.661975] device k1806-YcXLF left promiscuous mode # qemu-system-x86_64 --version QEMU emulator version 4.2.0 (qemu-4.2.0-2.fc31) Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers # virsh -V Virsh command line tool of libvirt 6.0.0 See web site at https://libvirt.org/ Compiled with support for: Hypervisors: QEMU/KVM LXC LibXL OpenVZ VMware VirtualBox ESX Hyper-V Test Networking: Remote Network Bridging Interface netcf Nwfilter VirtualPort Storage: Dir Disk Filesystem SCSI Multipath iSCSI LVM RBD Sheepdog Gluster ZFS Miscellaneous: Daemon Nodedev SELinux Secrets Debug DTrace Readline After that the partition table of the zfs volume was cleared. I also opened a bug report with all informations i could get so far: https://bugzilla.redhat.com/show_bug.cgi?id=1795082 I am thankful for any idea / suggestion. Thank you ! -- Mit freundlichen Gruessen / Best regards Oliver Dzombic Layer7 Networks mailto:info@layer7.net Anschrift: Layer7 Networks GmbH Zum Sonnenberg 1-3 63571 Gelnhausen HRB 96293 beim Amtsgericht Hanau Geschäftsführung: Oliver Dzombic UST ID: DE259845632

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