Intel's VMCS includes a TSC offset field as well as TSC scaling. These allow for a stable RDTSC across migrations between hosts, modulo actual time lost to migration blackout.
(I work on virtualization in GCE)
(I work on virtualization in GCE)
But I only skimmed this and I don't see that it mentions about migration across hosts. Only that the hypervisor is able to expose the MSRs or PMCs.
---
[1] Not all of the clock_gettime sources hit the vDSO even on bare metal Linux on typical x86 hardware, but many of the important ones do.