When migrating a domain with invtsc CPU feature enabled, the TSC frequency of the destination host must match the frequency used when the domain was started on the source host or the destination host has to support TSC scaling. If the frequencies do not match and the destination host does not support TSC scaling, QEMU will fail to set the right TSC frequency when starting vCPUs on the destination and thus migration will fail. However, this is quite late since both host might have spent significant time transferring memory and perhaps even storage data. By adding the check to libvirt we can let migration fail before any data starts to be sent over. If for some reason libvirt is unable to detect the host's TSC frequency or scaling support, we'll just let QEMU try and the migration will either succeed or fail later. Luckily, we mandate TSC frequency to be explicitly set in the domain XML to even allow migration of domains with invtsc. We can just check whether the requested frequency is compatible with the current host before starting QEMU. And to let libvirt client decide whether it should even start the migration to a specific host, this series adds host's TSC frequency and scaling support to the host CPU capabilities XML. https://bugzilla.redhat.com/show_bug.cgi?id=1641702 Jiri Denemark (5): util: Add virHostCPUGetTscInfo conf: Report TSC frequency in host CPU capabilities cpu_x86: Fix placement of *CheckFeature functions cpu_x86: Probe TSC frequency and scaling support qemu: Check TSC frequency before starting QEMU src/conf/cpu_conf.c | 48 ++++++++++++++++++++++++ src/conf/cpu_conf.h | 2 + src/cpu/cpu_x86.c | 81 ++++++++++++++++++++++------------------- src/qemu/qemu_process.c | 53 +++++++++++++++++++++++++++ src/util/virhostcpu.c | 71 ++++++++++++++++++++++++++++++++++++ src/util/virhostcpu.h | 11 ++++++ 6 files changed, 229 insertions(+), 37 deletions(-) -- 2.21.0 -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
