Re: [PATCH v2 14/17] kvm: x86: Introduce kvmclock device to save/restore its state

Glauber Costa
2011-01-03T16:38:39Z

On Mon, 2011-01-03 at 18:04 +0200, Avi Kivity wrote:
> On 01/03/2011 10:33 AM, Jan Kiszka wrote:
> > From: Jan Kiszka<jan.kiszka@siemens.com>
> >
> > If kvmclock is used, which implies the kernel supports it, register a
> > kvmclock device with the sysbus. Its main purpose is to save and restore
> > the kernel state on migration, but this will also allow to visualize it
> > one day.
> >
>
> kvmclock is a per-cpu affair.
>
> >
> > @@ -534,6 +599,10 @@ int kvm_arch_init(int smp_cpus)
> > int ret;
> > struct utsname utsname;
> >
> > +#ifdef KVM_CAP_ADJUST_CLOCK
> > + sysbus_register_withprop(&kvmclock_info);
> > +#endif
> > +
>
> So this doesn't look right. I think we're fine with just migrating the
> MSRs, like we migrate anything else that has to do with the cpu.

The ioctl jan is handling here is a global one, that adjusts the base
offset for the clock over migration. It is okay.