Hi Lukas, I using Libvirt `snapshot-create-as` and then `restore`. On restore I get the following errors:
qemu-system-x86_64: warning: TSC frequency mismatch between VM (3191999 kHz) and host (3191998 kHz), and TSC scaling unavailable qemu-system-x86_64: kvm_init_vcpu failed: Invalid argument I’m using Fedora CoreOS version 33, qemu 5.1, libvirt 6.6 Thanks, Veselina > On Dec 17, 2020, at 6:17 PM, Lukas Straub <lukasstra...@web.de> wrote: > > On Thu, 17 Dec 2020 14:04:03 +0200 > Veselina Radeva <ve...@st6.io> wrote: > >> Hi, >> >> I'm trying to migrate a VM from one host to another where there is a 1KHz >> difference in the TSC frequency between hosts. This results in errors >> caused by this warning >> <https://github.com/qemu/qemu/blob/b785d25e91718a660546a6550f64b3c543af7754/target/i386/kvm.c#L777>, >> so migration fails. On the other hand, I can see few lines before that >> <https://github.com/qemu/qemu/blob/b785d25e91718a660546a6550f64b3c543af7754/target/i386/kvm.c#L761> >> that >> there is a try to allow TSC frequency difference between host and VM if it >> falls within the specified bounds. It seems like `KVM_SET_TSC_KHZ`succeeds >> only when TSC Scaling is available >> <https://github.com/qemu/qemu/blob/2c6605389c1f76973d92b69b85d40d94b8f1092c/linux-headers/linux/kvm.h#L1361>. >> Practically this means that migration between hosts having difference in >> TSC frequency, even when it falls within bounds, is possible only when TSC >> scaling is available. >> >> On the other hand, in libvirt, >> <https://github.com/libvirt/libvirt/commit/d8e5b4560006590668d4669f54a46b08ec14c1a2> >> migration >> is allowed if TSC frequency difference falls within bounds, no matter if >> TSC scaling is enabled or not. >> >> So, I was wondering is it intended not to allow migration between hosts >> having differences in TSC frequency if TSC scaling is not available? Or is >> it a bug? >> >> Thanks in advance, >> Veselina Radeva >> https://st6.io/ > > Hi, > AFAIK, this is just a warning. I get it too and migration works fine here. > How exactly is migration failing for you? > > Regards, > Lukas Straub > > -- >
