Re: [Qemu-devel] [RFC][PATCH 1/2] kvm: Introduce basic MSI support in-kernel irqchips

[Avi Kivity]

On 03/28/2012 01:54 PM, Jan Kiszka wrote:
> > 
> >>>
> >>>> interface transparent. We create those routes on demand and keep them
> >>>> in a hash table. Succeeding messages can then search for an existing
> >>>> route in the table first and reuse it whenever possible. If we should
> >>>> run out of limited GSIs, we simply flush the table and rebuild it as
> >>>> messages are sent.
> >>>>
> >>>> This approach is rather simple and could be optimized further. However,
> >>>> it is more efficient to enhance the KVM API so that we do not need this
> >>>> clumsy dynamic routing over futures kernels.
> >>>
> >>> Two APIs are clumsier than one.
> >>
> >> The current one is very clumsy for user-injected MSIs while the new one
> >> won't be. It will also be very simple it implement if you recall the
> >> patch. I think that is worth it.
> > 
> > Don't see why.  The clumsiness will be retained.  The cpu doesn't care
> > how clumsy the API is, only the reader.
>
> We won't have to do any hashing/caching over the new API, just a plain
> "deliver this MSI" IOCTL. Specifically all our upcoming archs like Power
> and ARM will be able to take the shiny highway instead of the winding
> countryside road.

Upcoming archs are a good card to play.  However that code will remain
for x86, and there's nothing arch specific about it, is there?

> > 
> >>> wet the patch itself, suggest replacing the home grown hash with
> >>> http://developer.gnome.org/glib/2.30/glib-Caches.html.   
> >>
> >> Let's keep it simple :). We have no need for many of those features, and
> >> it would not be possible to implement the logic as compact as it is
> >> right now.
> > 
> > Due to the callbacks?
>
> Yep. That API pays of if you have more iterations and insertions/removals.

Okay, will wait for std::unordered_map<>.

-- 
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