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

[Avi Kivity]

On 03/28/2012 01:33 PM, Jan Kiszka wrote:
> On 2012-03-28 13:09, Avi Kivity wrote:
> > On 03/22/2012 01:17 AM, Jan Kiszka wrote:
> >> From: Jan Kiszka <address@hidden>
> >>
> >> This patch basically adds kvm_irqchip_send_msi, a service for sending
> >> arbitrary MSI messages to KVM's in-kernel irqchip models.
> >>
> >> As the current KVI API requires us to establish a static route from a
> > 
> > s/KVI/KVM/
> > 
> >> pseudo GSI to the target MSI message and inject the MSI via toggling
> >> that GSI, we need to play some tricks to make this unfortunately
> > 
> > s/unfortunately/unfortunate/
>
> Will fix these.

Only needed if you end up reposting.

> > 
> >> 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.

>
> > 
> > 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?

What if the code grows?

-- 
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