Re: [PATCH v4 2/2] KVM: VMX: Add Posted Interrupt supporting

[Gleb Natapov <gleb@redhat.com>]

On Mon, Feb 25, 2013 at 11:04:25AM +0000, Zhang, Yang Z wrote:
> Gleb Natapov wrote on 2013-02-25:
> > On Mon, Feb 25, 2013 at 08:42:52AM +0000, Zhang, Yang Z wrote:
> >> Avi Kivity wrote on 2013-02-25:
> >>> I didn't really follow, but is the root cause the need to keep track
> >>> of interrupt coalescing?  If so we can recommend that users use
> >>> KVM_IRQ_LINE when coalescing is unneeded, and move interrupt injection
> >>> with irq coalescing support to vcpu context.
> >> So we can hide the capability KVM_CAP_IRQ_INJECT_STATUS when posted
> > interrupt is enabled to force users doesn't to use KVM_IRQ_LINE_STATUS. Does
> > this acceptable?
> >> 
> >> The only case in KVM that need to know the interrupt injection status is vlapic
> > timer. But since vlapic timer and vcpu are always in same pcpu, so there is no
> > problem.
> >> 
> > Not really. The primary user of this interface is RTC interrupt
> > re-injection for Windows guests.
> So without KVM_IRQ_LINE_STATUS capability, RTC cannot work well?
> 
Windows guests may experience timedrift under CPU overcommit scenario.

--
			Gleb.