Re: [PATCH v2 0/5] ioapic/lapic/msi cleanup

[Gleb Natapov <gleb@redhat.com>]

On Thu, Mar 05, 2009 at 07:34:36PM -0300, Marcelo Tosatti wrote:
> On Thu, Mar 05, 2009 at 04:34:38PM +0200, Gleb Natapov wrote:
> > There are many code/logic duplications throughout ioapic/lapic/msi device
> > emulation. Try to consolidate as much code as possible.
> > 
> > ---
> > 
> > Gleb Natapov (5):
> >       Get rid of deliver_bitmask.
> >       Change the way how lowest priority vcpu is calculated.
> >       Consolidate ioapic/ipi interrupt delivery logic.
> >       ioapic/msi interrupt delivery consolidation.
> >       Make kvm_apic_set_irq() deliver all kinds of interrupts.
> 
> Applied and pushed, thanks.
> 
> There is one issue with the new low prio selection though. Say you have
> an interrupt whose load is shared between all vcpus in the guest. 
> 
> The first vcpu which has its counter overflowed will then handle the int
> load by itself until it approximates to the counter of the other vcpus.
> 
I took this in account. The priority counter is signed, so if say vcpu1
counter is overflows to 0x7fffffff + 1 and the vcpu2 counter is still
0x7fffffff then vcpu1 - vcpu2 = 1 and vcpu2 will be chosen to deliver
interrupts.

> Same happens with cpu hotplug.
> 
For got about hotplug :(

> Not sure that the best way is to fix that. Perhaps reset all online     
> vcpus to 0 on overflow/cpu-hotplug ?
> 
Yes, rest counters on hotplug should work and is rare event.

> Or max the counter to a smaller value like 64 or something.
I'll try this and see how well interrupts will be spread between CPUs.

--
			Gleb.