On Mon, Nov 14, 2016 at 02:54:38PM +0100, Paolo Bonzini wrote:
>
>
> On 14/11/2016 13:36, Marcelo Tosatti wrote:
> > + /* local (running VM) restore */
> > + if (s->clock_valid) {
> > + /*
> > + * if host does not support reliable KVM_GET_CLOCK,
> > + * read kvmclock value from memory
> > + */
> > + if (!kvm_has_adjust_clock_stable()) {
> > + time_at_migration = kvmclock_current_nsec(s);
>
> Just assign to s->clock here...
If kvmclock is not enabled, you want to use s->clock,
rather than 0.
> > + }
> > + /* migration/savevm/init restore */
> > + } else {
> > + /*
> > + * use s->clock in case machine uses reliable
> > + * get clock and host where vm was executing
> > + * supported reliable get clock
> > + */
> > + if (!s->mach_use_reliable_get_clock ||
> > + !s->src_use_reliable_get_clock) {
> > + time_at_migration = kvmclock_current_nsec(s);
>
> ... and here, so that time_at_migration is not needed anymore.
Same as above.
> Also here it's enough to look at s->src_user_reliable_get_clock, because
> if s->mach_use_reliable_get_clock is false,
> s->src_use_reliable_get_clock will be false as well.
Yes, but i like the code annotation.
> > + }
> > + }
> >
> > - /* We can't rely on the migrated clock value, just discard it */
> > + /* We can't rely on the saved clock value, just discard it */
> > if (time_at_migration) {
> > s->clock = time_at_migration;
>
> [...]
>
> >
> > +static bool kvmclock_src_use_reliable_get_clock(void *opaque)
> > +{
> > + KVMClockState *s = opaque;
> > +
> > + /*
> > + * On machine types that support reliable KVM_GET_CLOCK,
> > + * if host kernel does provide reliable KVM_GET_CLOCK,
> > + * set src_use_reliable_get_clock=true so that destination
> > + * avoids reading kvmclock from memory.
> > + */
> > + if (s->mach_use_reliable_get_clock && kvm_has_adjust_clock_stable()) {
> > + s->src_use_reliable_get_clock = true;
> > + }
> > +
> > + return s->src_use_reliable_get_clock;
> > +}
>
> Here you can just return s->mach_use_reliable_get_clock.
mach_use_reliable_get_clock can be true but host might not support it.
> To set
> s->src_use_reliable_get_clock, after issuing KVM_GET_CLOCK you can look
> at the KVM_CLOCK_TSC_STABLE bit in the kvm_clock struct's flags.
KVM_CLOCK_TSC_STABLE bit in the kvmclock structure !=
KVM_GET_CLOCK returns reliable value, right?
> You don't actually need kvm_has_adjust_clock_stable(), but please place
> the KVM_GET_CLOCK code for kvmclock_pre_save and
> kvmclock_vm_state_change in a common function.
Sure.
> Also, just another small nit: please make your scripts use the "-p"
> option on diff. :)
Sure.
>
> Thanks,
>
> Paolo
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