Re: [Qemu-devel] [PATCH 5/8] [PATCH RFC v2] s390-qemu: cpu hotplug - Introduce post-cpu-init function

["Jason J. Herne" <jjherne@linux.vnet.ibm.com>]

On 06/08/2013 06:10 PM, Andreas Färber wrote:
> Am 07.06.2013 19:28, schrieb Jason J. Herne:
>> From: "Jason J. Herne" <jjherne@us.ibm.com>
>>
>> In preparation for treating cpus as devices
>
> CPUs *are* devices since multiple releases now, so this is badly put.
>
>> we need to separate machine
>> initialization into two stages:
>> 1. Initialization that needs to be done before cpu devices can be created.
>> 2. Initialization that requires cpu devices to already be created.
>>
>> This is accomplished by creating an optional post-cpu initialization function
>> for QEMUMachine.
>
> Whatever you are using it for, this sounds wrong to me.
>

The QEMUMachine->init() function (at least for S390) currently handles 
several tasks.  One of those tasks is the creation of cpus.  If we are 
switching to a new paradigm where QOM cpu devices are parsed and created 
in main() then QEMUMachine->init() will happen either before or after 
cpus are created.  This change is meant to split QEMUMachine->init() 
into two parts

1. Stuff that does not depend on cpu creation. Specifically, stuff that 
might be a dependency of cpu create, like allocating ipi_states.

2. Stuff that does depend on cpu creation.  Like 
vm_s390_enable_css_support() which requires CPU 0 to exist.


> Machine init is supposed to use less code and more QOM infrastructure,
> with a future goal of replacing most code with a config file
> instantiating and wiring up devices.
>

Duly noted.  I can have another look at the code.  Perhaps there is an 
easy place I can move the ipi_state initialization.  Also, perhaps there 
is a way to remove the cpu-0 dependency from 
vm_s390_enable_css_support().  Both of these changes would remove the 
need for the post_cpu_init function.

> And please don't forget to CC me on the next CPU series.
>

Sorry.  I had meant to CC you originally.

-- 
-- Jason J. Herne (jjherne@linux.vnet.ibm.com)