On Sun, Aug 05, 2012 at 04:33:02PM +0300, Avi Kivity wrote:
> On 08/05/2012 03:58 PM, Gleb Natapov wrote:
> > APIC code has a lot of checks for apic presence and apic HW/SW enable
> > state. Most common configuration is when each vcpu has in kernel apic
> > and it is fully enabled. This path series uses jump labels to turn checks
> > to nops in the common case.
> >
> > Gleb Natapov (8):
> > KVM: clean up kvm_(set|get)_apic_base
> > KVM: use kvm_lapic_set_base() to change apic_base
> > KVM: mark apic enabled on start up.
> > Export jump_label_rate_limit()
> > KVM: use jump label to optimize checking for HW enabled APIC in
> > APIC_BASE MSR.
> > KVM: use jump label to optimize checking for SW enabled apic in
> > spurious interrupt register
> > KVM: use jump label to optimize checking for in kernel local apic
> > presence.
> > KVM: inline kvm_apic_present() and kvm_lapic_enabled()
>
> Neat.
>
> During guest boot up, some of these jump keys will change, no? Does
> this mean a stop_machine() or equivalent? I'm worried about real-time
> response or one guest being affected by another.
>
Yes, SW enable bit changes during boot. The jump label triggerable by a
guest are rate limited though. So stop machine will not happen more then
once per second even with malicious guests.
--
Gleb.
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