To attach to the hypervisor, kvmclock needs to write a per-CPU MSR.
When EARLY_AP_STARTUP is not defined, device attach happens too early:
APs are not yet spun up, so smp_rendezvous only runs the callback on the
local CPU. As a result, the timecounter only gets initialized on the
BSP, and then timekeeping is broken on SMP systems.
Implement handling for !EARLY_AP_STARTUP kernels: keep track of the CPU
on which device attach ran, and then use a SI_SUB_SMP SYSINIT to
register the rest of the CPUs with the hypervisor.
Reported by: Shrikanth R Kamath <kshrikanth@juniper.net>
Reviewed by: kib, jhb (earlier versions)
Sponsored by: Klara, Inc.
Sponsored by: Juniper Networks, Inc.
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D37705
An interface was added to derive an implied TSC frequency from pvclock
in 2015, but this interface was never exposed anywhere user-visible.
Reviewed by: kib, bryanv
Differential Revision: https://reviews.freebsd.org/D32974
Add support for the KVM paravirtual clock device.
Sponsored by: Juniper Networks, Inc.
Sponsored by: Klara, Inc.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D29733