2015-01-09 15:56+0100, Paolo Bonzini:
>
>
> On 09/01/2015 15:54, Radim Krčmář wrote:
> > There are two points relevant to this patch in new KVM's implementation,
> > ("KVM: x86: amend APIC lowest priority arbitration",
> > https://lkml.org/lkml/2015/1/9/362)
> >
> > 1) lowest priority depends on TPR
> > 2) there is no need for balancing
> >
> > (1) has to be considered with PI as well.
>
> The chipset doesn't support it. :(
I meant that we need to recompute PI entries for lowest priority
interrupts every time guest's TPR changes.
Luckily, Linux doesn't use TPR, but other OS might be a reason to drop
lowest priority from PI optimizations. (Or make it more complicated.)
> > I kept (2) to avoid whining from people building on that behaviour, but
> > lowest priority backed by PI could be transparent without it.
> >
> > Patch below removes the balancing, but I am not sure this is a price we
> > allowed ourselves to pay ... what are your opinions?
>
> I wouldn't mind, but it requires a lot of benchmarking.
(I was afraid it would come to that.)
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