Re: [Qemu-devel] [RFC] in-kernel irqchip : split devices

[Avi Kivity <avi@redhat.com>]

On 10/14/2009 04:30 PM, Glauber Costa wrote:
> Hello people,
>
> As I promised, I am sending a very brief PoC wrt split devices and in-kernel irqchip.
> In this mail, I am including only the ioapic version for apreciation. I also have i8259,
> and apic will take me a little bit more. This is just to try to bind the discussion to real
> code.
>
>    

I still can't say I like it.  The reset function is duplicated, the 
state representation (which is an ABI) is gratuitously forked.

You can't save/restore in-kernel irqchip and userspace irqchip, even 
though where the code is located is an implementation detail.  While we 
may not care much for the ioapic, it sets a bad precedent for vhost-net, 
where we'd like to migrate from non-vhost-net hosts to vhost-net hosts 
without the user noticing anything.

> Note that we end up with a very slim representation of the device, and the code is much less
> confusing, IMHO.
>    

You can always remove if statements by duplicating the code and pushing 
the if one level upwards.  In total, there is more code, and it is more 
confusing (since you need to deal with implementation details at a 
higher level).

-- 
error compiling committee.c: too many arguments to function