Re: [PATCH v2] KVM: x86: Remove support for reporting coalesced APIC IRQs

[Gleb Natapov <gleb@redhat.com>]

On Mon, May 13, 2013 at 10:30:33PM -0300, Marcelo Tosatti wrote:
> On Thu, May 02, 2013 at 10:14:32PM -0300, Marcelo Tosatti wrote:
> > On Sun, Apr 28, 2013 at 02:00:41PM +0200, Jan Kiszka wrote:
> > > From: Jan Kiszka <jan.kiszka@siemens.com>
> > > 
> > > Since the arrival of posted interrupt support we can no longer guarantee
> > > that coalesced IRQs are always reported to the IRQ source. Moreover,
> > > accumulated APIC timer events could cause a busy loop when a VCPU should
> > > rather be halted. The consensus is to remove coalesced tracking from the
> > > LAPIC.
> > > 
> > > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> > > ---
> > > 
> > > Changes in v2:
> > >  - preserve return values where we need to count to how many VCPUs an
> > >    IRQ was delivered
> > 
> > It would be best to confirm first that no guest depends on LAPIC timer
> > reinjection (rather than wait for guests to break and spend time
> > debugging). Specially since such kind of bugs are not easy to pinpoint.
> > Or if there is evidence to invalidate such reasoning, please point it
> > out.
> > 
> > Honestly i don't recall: would have to check RHEL5.32 UP/SMP, RHEL5.64
> > UP/SMP, RHEL4.32, RHEL4.64, RHEL6. Can do that in a week or so.
> 
> Its OK to remove LAPIC timer reinjection.
Applied. Thanks for checking!

--
			Gleb.