Re: [PATCH v4] KVM: Introduce direct MSI message injection for in-kernel irqchips

[Avi Kivity <avi@redhat.com>]

On 04/04/2012 12:22 PM, Jan Kiszka wrote:
> > 
> >>> Until we do have this fast path we can just fill this value with zeros,
> >>> so kernel patch (almost) does not need to change for this -
> >>> just the header.
> >>
> >> Partially implemented interfaces invite breakage.
> > 
> > Hmm true. OK scrap this idea then, it's not clear
> > whether we are going to optimize this anyway.
> > 
>
> Also, the problem is that keeping that ID in userspace requires an
> infrastructure like the MSIRoutingCache that I proposed originally. Not
> much won /wrt invasiveness there. 

Internal qemu refactorings are not a driver for kvm interface changes.

> So we should really do the routing
> optimization in the kernel - one day.

No, we need to make a choice:

explicit handles: array lookup, more expensive setup
no handles: hash loopup, more expensive, but no setup, and no artificial
limits

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.