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SubjectRe: [PATCH v10 2/2] kvm: Add resampling irqfds for level triggered interrupts
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On Wed, 2012-09-19 at 12:10 +0300, Avi Kivity wrote:
> On 09/19/2012 12:08 PM, Michael S. Tsirkin wrote:
>
> >> Whoa. Can't we put the resampler entry somewhere we don't need to
> >> search for it? Like a kvm_kernel_irq_routing_entry, that's indexed by
> >> gsi already (kvm_irq_routing_table::rt_entries[gsi]).
> >
> > I'm not sure why would we bother optimizing this,
>
> Not optimizing, simplifying.
>
> > but if we do, I guess we could look for the irq notifier
> > which is already indexed by gsi.
>
> It's not, it's looked up in a list.


I'm not sure it's a simplification because to index by gsi we suddenly
need to care how many gsis there are. I believe that currently means we
have to assume an ioapic. Creating a dumb list is a little bit of
overhead, but we get to stay blissfully unaware of the gsi
implementation. Practically we're looking at a list of 4 entries, maybe
a few times that when we expose more PCI root bridges to the guest.
Thanks,

Alex



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