Re: [PATCH] KVM: x86: Avoid busy loops over uninjectable pending APIC timers

[Gleb Natapov <gleb@redhat.com>]

On Thu, Mar 21, 2013 at 05:51:50PM -0300, Marcelo Tosatti wrote:
> > > > But current PI patches do break them, thats my point. So we either
> > > > need to revise them again, or drop LAPIC timer reinjection. Making
> > > > apic_accept_irq semantics "it returns coalescing info, but only sometimes"
> > > > is dubious though.
> > > We may rollback to the initial idea: test both irr and pir to get coalescing info. In this case, inject LAPIC timer always in vcpu context. So apic_accept_irq() will return right coalescing info.
> > > Also, we need to add comments to tell caller, apic_accept_irq() can ensure the return value is correct only when caller is in target vcpu context.
> > > 
> > We cannot touch irr while vcpu is in non-root operation, so we will have
> > to pass flag to apic_accept_irq() to let it know that it is called
> > synchronously. While all this is possible I want to know which guests
> > exactly will we break if we will not track interrupt coalescing for
> > lapic timer. If only 2.0 smp kernels will break we can probably drop it.
> 
> RHEL4 / RHEL5 guests.
RHEL5 has kvmclock no? We should not break RHEL4 though.

--
			Gleb.