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9p file sharing issue
by Johan 19 Jul '20

19 Jul '20

I've run into an issue with 9p file sharing that I suspect is a bug. I'm running some Debian ARM VMs (armhf Ubuntu guests on an aarch64 Debian stretch host in case that matters). I'm using direct kernel boot, so I'm also using 9p host file sharing so that kernel updates from within the guest would work. However, I've noticed that dpkg (the Debian/Ubuntu package manager) fails when writing into a /boot directory that's shared from the host via 9p. Some investigation reveals that this is because dpkg does an openat() call of the type openat(AT_FDCWD, "/boot/vmlinuz-4.15.0-111-generic-lpae.dpkg-new", O_WRONLY|O_CREAT|O_EXCL|O_LARGEFILE, 000); and that it's the 0 permissions mode (last parameter) that causes the call to fail with a "Permission denied" error. A simple test program that does the above openat() call but with another mode (say, 600) works just fine. Some further data: * QEMU runs as the unprivileged user libvirt-qemu (Debian default) * QEMU is version 2.8, libvirt version 3.0.0 * XML snippet for 9p setup: <filesystem type='mount' accessmode='squash'> <source dir='/host/path/boot-test9p'/> <target dir='boot_mount'/> <alias name='fs0'/> <address type='pci' domain='0x0000' bus='0x03' slot='0x01' function='0x0'/> </filesystem> * The 9p filesystem is mounted by this line in /etc/fstab on the guest: boot_mount /boot 9p rw,dirsync,_netdev,relatime,trans=virtio,version=9p2000.L 0 0 The essential problem seems to be that opening a file with a mode of 0 is not compatible with the "squash" 9p access mode. Is this expected? Thank you, Johan

1 0

Unable to decode message length
by Valentin David 16 Jul '20

16 Jul '20

Hello all, I have been trying to get libvirtd to work but when I connect to it with virsh, I get "error : virNetMessageDecodeLength:131 : Unable to decode message length" This happens with libvirt 6.1.0, libtirpc 1.2.6, rpcsvc-proto 1.4.1. I have tried with other versions, but I still get the same error. If anybody has any tip on what to try next, that would be helpful. Thank you in advance. Here is the debug log of libvirtd when I try to connect with virsh: 2020-07-14 16:29:58.220+0000: 5352: info : virEventGLibHandleDispatch:116 : EVENT_GLIB_DISPATCH_HANDLE: watch=2 events=1 cb=0x7f7b55b86c50 opaque=0x556fbcf8b8a0 2020-07-14 16:29:58.220+0000: 5352: info : virObjectNew:250 : OBJECT_NEW: obj=0x556fbcf8d770 classname=virNetSocket 2020-07-14 16:29:58.220+0000: 5352: info : virNetSocketNew:278 : RPC_SOCKET_NEW: sock=0x556fbcf8d770 fd=18 errfd=-1 pid=0 localAddr=127.0.0.1;0, remoteAddr=127.0.0.1;0 2020-07-14 16:29:58.220+0000: 5352: info : virObjectNew:250 : OBJECT_NEW: obj=0x556fbcf8da50 classname=virNetServerClient 2020-07-14 16:29:58.220+0000: 5352: info : virObjectRef:385 : OBJECT_REF: obj=0x556fbcf8d770 2020-07-14 16:29:58.220+0000: 5352: info : virEventGLibTimeoutAdd:341 : EVENT_GLIB_ADD_TIMEOUT: timer=1 interval=-1 cb=0x7f7b55b8d490 opaque=0x556fbcf8da50 ff=(nil) 2020-07-14 16:29:58.220+0000: 5352: info : virNetServerClientNewInternal:421 : RPC_SERVER_CLIENT_NEW: client=0x556fbcf8da50 sock=0x556fbcf8d770 2020-07-14 16:29:58.220+0000: 5352: info : virObjectRef:385 : OBJECT_REF: obj=0x556fbcf8da50 2020-07-14 16:29:58.220+0000: 5352: info : virObjectRef:385 : OBJECT_REF: obj=0x556fbcf8d770 2020-07-14 16:29:58.220+0000: 5352: info : virEventGLibHandleAdd:160 : EVENT_GLIB_ADD_HANDLE: watch=11 fd=18 events=1 cb=0x7f7b55b86c50 opaque=0x556fbcf8d770 ff=0x7f7b55b86c00 2020-07-14 16:29:58.220+0000: 5352: info : virObjectRef:385 : OBJECT_REF: obj=0x556fbcf8da50 2020-07-14 16:29:58.220+0000: 5352: info : virNetServerCheckLimits:280 : Re-enabling services 2020-07-14 16:29:58.220+0000: 5352: info : virEventGLibHandleUpdate:194 : EVENT_GLIB_UPDATE_HANDLE: watch=2 events=1 2020-07-14 16:29:58.220+0000: 5352: info : virObjectNew:250 : OBJECT_NEW: obj=0x556fbcf8e330 classname=virKeepAlive 2020-07-14 16:29:58.220+0000: 5352: info : virKeepAliveNew:208 : RPC_KEEPALIVE_NEW: ka=0x556fbcf8e330 client=0x556fbcf8da50 2020-07-14 16:29:58.220+0000: 5352: info : virObjectRef:385 : OBJECT_REF: obj=0x556fbcf8da50 2020-07-14 16:29:58.220+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8da50 2020-07-14 16:29:58.220+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8d770 2020-07-14 16:29:58.220+0000: 5352: info : virEventGLibHandleDispatch:116 : EVENT_GLIB_DISPATCH_HANDLE: watch=11 events=1 cb=0x7f7b55b86c50 opaque=0x556fbcf8d770 2020-07-14 16:29:58.220+0000: 5352: error : virNetMessageDecodeLength:131 : Unable to decode message length 2020-07-14 16:29:58.220+0000: 5352: info : virKeepAliveStop:300 : RPC_KEEPALIVE_STOP: ka=0x556fbcf8e330 client=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virObjectRef:385 : OBJECT_REF: obj=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8e330 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:349 : OBJECT_DISPOSE: obj=0x556fbcf8e330 2020-07-14 16:29:58.221+0000: 5352: info : virKeepAliveDispose:221 : RPC_KEEPALIVE_DISPOSE: ka=0x556fbcf8e330 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virObjectRef:385 : OBJECT_REF: obj=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virEventGLibHandleRemove:261 : EVENT_GLIB_REMOVE_HANDLE: watch=11 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8d770 2020-07-14 16:29:58.221+0000: 5352: info : virNetServerCheckLimits:280 : Re-enabling services 2020-07-14 16:29:58.221+0000: 5352: info : virEventGLibHandleUpdate:194 : EVENT_GLIB_UPDATE_HANDLE: watch=2 events=1 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virEventGLibHandleRemoveIdle:242 : EVENT_GLIB_REMOVE_HANDLE_IDLE: watch=11 ff=0x7f7b55b86c00 opaque=0x556fbcf8d770 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:349 : OBJECT_DISPOSE: obj=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virNetServerClientDispose:976 : RPC_SERVER_CLIENT_DISPOSE: client=0x556fbcf8da50 2020-07-14 16:29:58.221+0000: 5352: info : virEventGLibTimeoutRemove:437 : EVENT_GLIB_REMOVE_TIMEOUT: timer=1 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:347 : OBJECT_UNREF: obj=0x556fbcf8d770 2020-07-14 16:29:58.221+0000: 5352: info : virObjectUnref:349 : OBJECT_DISPOSE: obj=0x556fbcf8d770 2020-07-14 16:29:58.221+0000: 5352: info : virNetSocketDispose:1332 : RPC_SOCKET_DISPOSE: sock=0x556fbcf8d770 2020-07-14 16:29:58.221+0000: 5352: info : virEventGLibTimeoutRemoveIdle:417 : EVENT_GLIB_REMOVE_TIMEOUT_IDLE: timer=1 ff=(nil) opaque=0x556fbcf8da50

2 3

SELinux labels change in libvirt
by Ram Lavi 16 Jul '20

16 Jul '20

Hello all, tl;dr, can you point me to the point in the libvirt repo where it's trying to change a tap-device's SELinux label? I am trying to create a tap device with libvirt on a super-privileged container, and then use it on another, unprivileged container with libvirt. User wise, I know I need the super-privileged container to open the tap device with the user of the unprivileged one - that I already did and it's not the issue. But I have a problem when I open the tap device in the non-privileged container: the tap device currently has the spc_t label since the tun_socket inherited the selinux context from the super-privileged container who creates it. then libvirt is trying to change the SELinux labels, and since it's not privileged then it fails. But I didn't find where and how libvirt is trying to change the tap device's label. Can you point me to that specific code on libvirt? Ram Lavi Senior Software Engineer Red Hat Israel <https://www.redhat.com/> Yerushalaim Road 34, Ra'anana ralavi(a)redhat.com IM: ralavi @RedHat <https://twitter.com/redhat> Red Hat <https://www.linkedin.com/company/red-hat> Red Hat <https://www.facebook.com/RedHatInc> <https://www.redhat.com/>

2 5

Help with external snapshots as backups
by Alex Regan 14 Jul '20

14 Jul '20

Hi, I have a win10 guest on a fedora32 system and have some questions as I explore using external snapshots as a form of backup in case of a Windows failure (as in, it won't boot or is completely irrecoverable) as well as revision control (to be able to rollback changes after a failed app install, etc). The first hit on Google for external snapshots involves a RHEL7 document that talks about how it's not officially supported. The current RHEL8 docs don't include any references to snapshots. The fedora docs I've found are many years old - I'm just not sure if they're still applicable. Where can I find the current docs for fedora32? - If I've already created a live internal snapshot, can I then create an external safely? Are all changes currently being written to this internal snapshot now? - Can external snapshots be used for backup? Perhaps there are predefined steps for doing this that I can follow? This is the procedure I'm currently using. I've made a backup of the original image - can I now just continue to backup the snapshots in the eventuality of a crash, then use this original image backup and the snapshots to restore it? I suppose I would also periodically merge the snapshots back into the a single snapshot to ease the process? # virsh snapshot-create-as --domain dave-win10a win10a-state01 --diskspec vda,file=/var/lib/libvirt/images/vm_snapshots/disk-overlay.qcow2,snapshot=external --memspec file=/var/lib/libvirt/images/vm_snapshots/mem-overlay.qcow2,snapshot=external --atomic Domain snapshot win10a-state01 created # ls -lh vm_snapshots/ total 3.3G -rw------- 1 qemu qemu 196K Jul 11 12:32 disk-overlay.qcow2 -rw------- 1 root root 3.3G Jul 11 12:32 mem-overlay.qcow2 Thanks, Alex

2 1

Emulated TPM devices and snapshots of running VMs
by Milan Zamazal 09 Jul '20

09 Jul '20

Hi, I would like to clarify how to make snapshots of running VMs with emulated TPM devices. As far as I understand QEMU documentation, it's possible to make snapshots of running VMs with TPM, but it's important to retain the state of swtpm. Does libvirt assist with that in any way or is it completely user's responsibility? libvirt pauses the VM internally when making a snapshot, which should be the right moment to copy the swtpm data, but the user doesn't have control over it. Is there a way to make a copy of swtpm data that is guaranteed to be consistent with the snapshot? Thank you, Milan

2 5

Could you please help with questions about the net failover feature
by Yalan Zhang 09 Jul '20

09 Jul '20

Hi laine, I have leave some questions on IRC, but my VPN broken time after time. Please ignore the questions on IRC. In my understanding, the standby and primary hostdev interface may be in different subnet. I'm not sure whether it is correct. Could you please help to explain? Thank you in advance. For example, primary hostdev is connected to vf-pool with <pf='eth0'/>, while the standby is connected to NAT network with " forward dev='eth0'". The standby interface will get ip as 192.168.122.x, but after NAT, it will be in the same subnet of the vf. So after the VF is unplugged, the packet will still broadcast in the same subnet, and the vm will get the packet as the standby share the same mac. Right? Thank you! ------- Best Regards, Yalan Zhang IRC: yalzhang

4 7

Why wireless interface cannot be attached to a Linux host bridge?
by ryotaro kobayashi 08 Jul '20

08 Jul '20

Hello, everyone. I'm from japan and using machine translation, so I apologize if it's hard to read. I am currently trying to build a virtual environment using Ubuntu and kvm. However, I found out from the following page that the virtual machine cannot use the bridge network because I am using a wireless network. https://wiki.libvirt.org/page/Networking I am having trouble with this because my PC is using a wireless LAN. On that page it says "wireless interfaces cannot be attached to a Linux host bridge", I Can you tell me why this is so? Is it a limitation of the NIC driver for the wireless LAN? Or is it a limitation of libvirt? Best regards.

6 9

Testing DKIM signatures
by dberrange＠yahoo.com 02 Jul '20

02 Jul '20

Please ignore this test message

2 1

Asking for suggestion and questions regarding the workings/internals of Libvirt
by Shashwat shagun 01 Jul '20

01 Jul '20

I am building a multi-tenant json REST API for managing KVM VMs but don't know if libvirt transactions are going to be fast enough to be invoked directly? or do i need a job queue? Does libvirtd already have a job queue that is used when handling time-consuming tasks like creating domain and such? If yes then what about tasks such as volUpload or download? Shashwat. shashwatshagun2581(a)gmail.com

1 0

Re: image of OS X how to boot
by Jerry Geis 01 Jul '20

01 Jul '20

Thanks Marc - I'll play. Jerry

1 0

Re: image of OS X how to boot
by Jerry Geis 01 Jul '20

01 Jul '20

Thanks - but I dont see scripts for Yosemite - which to use ? Jerry

2 1

Re: image of OS X how to boot
by Jerry Geis 01 Jul '20

01 Jul '20

Thanks Marc - my OSX is still Yosemite. I dont see that in these files ? Is support for that available ? Jerry

2 1

no/empty NUMA cells on domain XML
by Polina Agranat 01 Jul '20

01 Jul '20

Hi , I'm looking for a possibility to simulate a VM (to be used as a host) reporting no or empty NUMA <cells> in 'virsh capabilities'. 'virsh capabilities' usually reports single NUMA in the VMs, like <numa> <cell id='0' cpus='0-63' memory='16777216' unit='KiB'/> </numa> I appreciate if someone could advise Thank you Polina

2 2

image of OS X how to boot
by Jerry Geis 30 Jun '20

30 Jun '20

I have an image of OS X that I made with from the physical disk using dd. When I boot with libvirt-manager and environment I get an error. no bootable option or device was found. Using CentOS 8 host - I tried fdisk image.img and I no longer see any options there to toggle bootable partition option. How can I boot OSX ? Thanks, Jerry

2 1

plug pre-created tap devices to libvirt guests
by Miguel Duarte de Mora Barroso 30 Jun '20

30 Jun '20

Hi all, I'm aware that it is possible to plug pre-created macvtap devices to libvirt guests - tracked in RFE [0]. My interpretation of the wording in [1] and [2] is that it is also possible to plug pre-created tap devices into libvirt guests - that would be a requirement to allow kubevirt to run with less capabilities in the pods that encapsulate the VMs. I took a look at the libvirt code ([3] & [4]), and, from my limited understanding, I got the impression that plugging existing interfaces via `managed='no' ` is only possible for macvtap interfaces. Would you be able to shed some light into this ? Is it possible on libvirt-5.6.0 to plug pre-created tap devices to libvirt guests ? [0] - https://bugzilla.redhat.com/show_bug.cgi?id=1723367 [1] - https://bugzilla.redhat.com/show_bug.cgi?id=1723367#c2 [2] - https://bugzilla.redhat.com/show_bug.cgi?id=1723367#c3 [3] - https://github.com/libvirt/libvirt/blob/master/src/qemu/qemu_interface.c#L4… [4] - https://github.com/libvirt/libvirt/blob/master/src/qemu/qemu_interface.c#L4…

3 7

Do we need "amd_iommu=on" for AMD system anymore?
by Yalan Zhang 30 Jun '20

30 Jun '20

Hi, Since long time ago, to enable the SR-IOV VF pci passthrough function, I'm always adding "amd_iommu=on" into kernel cmdline on AMD system. But recently I found even I do not do this action, IOMMU is still enabled by kernel on AMD system. After searching, I found there is no such setting any more, refer to https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/ker… There are only 3 possible value as below: amd_iommu= fullflush off force_isolation Could anyone can help to confirm the changes? Thank you! And another question, it is said that the "iommu=pt" option is to improves IO performance for devices in the host, it is not a must for VF PCI passthrough, right? I'm not sure about the user cases. [Reference] 1. Reference about adding "amd_iommu=on", and it may be outdated: http://dpdk-guide.gitlab.io/dpdk-guide/setup/iommu.html 2. On AMD system without adding "amd_iommu=on" in the kernel cmdline, the iommu is enabled: # cat /proc/cmdline BOOT_IMAGE=(hd0,msdos1)/vmlinuz-4.18.0-193.el8.x86_64 root=/dev/mapper/rhel_hp--dl385g10--16-root ro crashkernel=auto resume=/dev/mapper/rhel_hp--dl385g10--16-swap rd.lvm.lv=rhel_hp-dl385g10-16/root rd.lvm.lv=rhel_hp-dl385g10-16/swap console=ttyS0,115200n81 # dmesg | grep -i iommu [ 3.712029] iommu: Default domain type: Passthrough [ 6.736019] pci 0000:00:00.2: IOMMU performance counters supported ... [ 6.780040] pci 0000:e0:00.2: IOMMU performance counters supported [ 6.786740] pci 0000:00:01.0: Adding to iommu group 0 [ 6.791876] pci 0000:00:01.1: Adding to iommu group 1 [ 6.797015] pci 0000:00:01.2: Adding to iommu group 2 [ 6.802150] pci 0000:00:01.4: Adding to iommu group 3 ... [ 7.866463] pci 0000:e0:00.2: Found IOMMU cap 0x40 [ 7.920222] perf/amd_iommu: Detected AMD IOMMU #0 (2 banks, 4 counters/bank). [ 7.927428] perf/amd_iommu: Detected AMD IOMMU #1 (2 banks, 4 counters/bank) ... ------- Best Regards, Yalan Zhang IRC: yalzhang

2 1

Virtual Bridge "Network" for Sandbox
by Paul O'Rorke 29 Jun '20

29 Jun '20

Hi all, I couldn't find any documentation on this, hopefully someone can point me in the right direction. I recently set up a sand-boxed environment for our developers. There are domain controller(s), workstations and servers in there. The whole thing is running on a single host using a "Virtual Network" defined in virt-manager on that host. Now I find I want to add more guests and there are not enough resources on this one host. Can I somehow make this Virtual Network available to two hosts? I do not want to move to a bridged network and have to physically join the two hosts with a discrete link when they are already on the same subnet at the host level. Is that possible? -- *Paul O'Rorke*

3 6

get contents of a storage volume in bytes
by Shashwat shagun 28 Jun '20

28 Jun '20

Hi, i have two machines with libvirt installed. I want to move a storage volume from the 1st machine to 2nd machine with code. I'm thinking of reading a storage volume into a byte array/stream then uploading through my own/custom handler (written in go) to the 2nd machine's custom handler which will then be writing the byte stream to libvirt storage volume. Is there a libvirt function to read storage volume into byte stream? Shashwat. shashwatshagun2581(a)gmail.com

3 2

RBD volume pools and locks
by Guy Godfroy 26 Jun '20

26 Jun '20

Hello, One of my libvirt cluster is using a RBD volume pool. I wish that I could configure libvirt lock manager to use RBD locks. Is that possible? I read here https://libvirt.org/kbase/locking.html that libvirt lock manager is shipped with 2 active plugins. Is there any other plugins that exist? Thanks. Guy Godfroy

1 0

virsh edit does not work when <initiator> and <auth> is used in config
by Fourhundred Thecat 25 Jun '20

25 Jun '20

Hello, I am having problem when using: "virsh edit <vm_name>" my VM has network iscsi disk defined: <disk type='network' device='disk'> <driver name='qemu' type='raw'/> <source protocol='iscsi' name='iqn.1992-08.com.netapp:5481.60080e50001ff2000000000051aee24d/0'> <host name='10.1.212.52' port='3260'/> <initiator> <iqn name='iqn.2013-01.bla.bla:01:test'/> </initiator> <auth username='myname'> <secret type='iscsi' usage='libvirtiscsi'/> </auth> </source> ... </disk> when I defined thje VM the first time, as always, libvirt reorders the lines in the XML config file as it likes. One of the reordering it did, was to put the "<initiator>" block above the "<auth>" block. But once I want to edit, "virsh edit <vm_name>", whatever change I make, even unrelated to iscsi disk, it reports error: error: XML document failed to validate against schema: Unable to validate doc against /usr/share/libvirt/schemas/domain.rng Extra element devices in interleave Element domain failed to validate content after long trial and error, I found I can finally save it when I reorder the "<initiator>" and "<auth>" blocks, so that "<auth>" is above "<initiator>". Once i save it, libvirt then reorders it back to the order, which will generate erro next time I attemt to edit. Anyway, this seems like a bug, and especially evil one. How could I get rid of this behaviour? thanks,

2 1

volume pool for LXC
by Guy Godfroy 23 Jun '20

23 Jun '20

Hello, Is it possible to use volume pools for LXC ? For instance LVM pools. It seems to be supporte by LXC bare commands. From the man page of lxc-create : -B, --bdev backingstore 'backingstore' is one of 'dir', 'lvm', 'loop', 'btrfs', 'zfs', 'rbd', or 'best'. The default is 'dir', meaning that the container root filesystem will be a directory under /var/lib/lxc/container/rootfs. This backing store type allows the optional --dir ROOTFS to be specified, meaning that the container rootfs should be placed under the specified path, rather than the default. (The 'none' backingstore type is an alias for 'dir'.) If 'btrfs' is specified, then the target filesystem must be btrfs, and the container rootfs will be created as a new subvolume. This allows snapshotted clones to be created, but also causes rsync --one-filesystem to treat it as a separate filesystem. If backingstore is 'lvm', then an lvm block device will be used and the following further options are available: --lvname lvname1 will create an LV named lvname1 rather than the default, which is the container name. --vgname vgname1 will create the LV in volume group vgname1 rather than the default, lxc. --thinpool thinpool1 will create the LV as a thin-provisioned volume in the pool named thinpool1 rather than the default, lxc. --fstype FSTYPE will create an FSTYPE filesystem on the LV, rather than the default, which is ext4. --fssize SIZE will create a LV (and filesystem) of size SIZE rather than the default, which is 1G. If backingstore is 'loop', you can use --fstype FSTYPE and --fssize SIZE as 'lvm'. The default values for these options are the same as 'lvm'. If backingstore is 'rbd', then you will need to have a valid configuration in ceph.conf and a ceph.client.admin.keyring defined. You can specify the following options : --rbdname RBDNAME will create a blockdevice named RBDNAME rather than the default, which is the container name. --rbdpool POOL will create the blockdevice in the pool named POOL, rather than the default, which is 'lxc'. If backingstore is 'best', then lxc will try, in order, btrfs, zfs, lvm, and finally a directory backing store.

1 0

qemu hook: event for source host too
by Guy Godfroy 23 Jun '20

23 Jun '20

Hello, this is my first time posting on this mailing list. I wanted to suggest a addition to the qemu hook. I will explain it through my own use case. I use a shared LVM storage as a volume pool between my nodes. I use lvmlockd in sanlock mode to protect both LVM metadata corruption and concurrent volume mounting. When I run a VM on a node, I activate the desired LV with exclusive lock (lvchange -aey). When I stop the VM, I deactivate the LV, effectively releasing the exclusive lock (lvchange -an). When I migrate a VM (both live and offline), the LV has to be activated on both source and target nodes, so I have to use a shared lock (lvchange -asy). That's why I need a hook event on the source host too (as far as I know after my tests, the migration event is only triggered on the target host). Is such a feature a possibility? Thanks for your attention. Guy Godfroy

2 13

Missing vnet interface in migration
by Ales Musil 22 Jun '20

22 Jun '20

Hi, in oVirt we have come across issue with a missing vnet interface (Original bug report [0]). This happened once in a huge batch of migrations e.g 2 failed out of 1200 and we came to conclusion that this is happening somewhere out of our control as libvirt reports: 2020-05-17 02:34:11,530+0000 ERROR (migsrc/623f6cc1) [virt.vm] (vmId='623f6cc1-d49f-43a4-8170-b5fec01f2897') operation failed: binding 'vnet54' is already being removed (migration:278) Unfortunately we don't have libvirt logs and producing them might not be possible. Is there anything else we can do to tackle down this issue? Thank you. Regards, Ales [0] https://bugzilla.redhat.com/1837395 -- Ales Musil Software Engineer - RHV Network Red Hat EMEA <https://www.redhat.com> amusil(a)redhat.com IM: amusil <https://red.ht/sig>

1 0

Feature request? Auto start vm upon next shutdown
by Marc Roos 22 Jun '20

22 Jun '20

Sometimes when you change the configuration, this configuration change will only be available after a shutdown. Not to have to monitor when the vm shuts down, to start it again. It could be nice to have libvirt start it one time. Something like: 1. change the network interface of a running guest 2. at the prompt of the virt-manager "Some changes may require a guest shutdown to take effect" introduce check box 'Auto start vm upon next shutdown' 3. shutdown the guest 4. after the guest completed shutdown, libvirt is automatically starting it again.

3 4

NVDIMM sizes and DIMM hot plug
by Milan Zamazal 19 Jun '20

19 Jun '20

Hi, I've found out that NVDIMM size and label size matter for regular (non-NV) DIMM hot plug. If the NVDIMM is not aligned correctly, the guest OS will not accept the hot plugged memory and will complain with messages such as Block size [0x8000000] unaligned hotplug range: start 0x225000000, size 0x10000000 The start address above is also reported within <memory> element of the hot plugged memory in the domain XML: <address type='dimm' slot='1' base='0x225000000'/> Apparently, in order to make memory hot plug working in the guest OS, the inserted memory must be aligned to the platform memory alignment (128 MB on x86_64). I'd like to clarify, how libvirt makes the DIMM address above. How is the NVDIMM memory range determined? According to my experiments, it seems the NVDIMM specified <size> is taken, NVDIMM <label> size is subtracted from it and the resulting value is reduced to the nearest multiple of NVDIMM <alignsize>. Is this observation correct? Is it guaranteed to be stable in future versions? I need to determine the right NVDIMM size to make the subsequent memory modules correctly aligned and then I can't change the NVDIMM size, to not damage data stored in the NVDIMM. Additionally, when adjusting maxMemory due to NVDIMM presence, should I increase it by the specified NVDIMM <size> or a different value? Thank you, Milan

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