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Re: [Qemu-devel] [PATCH 5/8] [PATCH RFC v2] s390-qemu: cpu hotplug - Int

From: Jason J. Herne
Subject: Re: [Qemu-devel] [PATCH 5/8] [PATCH RFC v2] s390-qemu: cpu hotplug - Introduce post-cpu-init function
Date: Mon, 10 Jun 2013 11:28:39 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6

On 06/08/2013 06:10 PM, Andreas Färber wrote:
Am 07.06.2013 19:28, schrieb Jason J. Herne:
From: "Jason J. Herne" <address@hidden>

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 (address@hidden)

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