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 --
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