From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH] KVM: x86: Avoid busy loops over uninjectable pending
 APIC timers
Date: Thu, 21 Mar 2013 20:06:41 -0300
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Cc: "Zhang, Yang Z" <yang.z.zhang@intel.com>,
	Jan Kiszka <jan.kiszka@web.de>, kvm <kvm@vger.kernel.org>
To: Gleb Natapov <gleb@redhat.com>
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On Thu, Mar 21, 2013 at 11:13:39PM +0200, Gleb Natapov wrote:
> 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.

kvmclock provides no timer interrupt... either LAPIC or PIT must be used
with kvmclock.