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

[Jan Kiszka]

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.

> 
>> 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.

> 
> 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.

Jan

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