Re: [Qemu-ppc] [PATCH 5/5] pseries: Move XICS initialization before cpu initialization

[Alexander Graf]

On 18.03.2013, at 03:55, David Gibson wrote:

> On Fri, Mar 15, 2013 at 01:33:18PM +0100, Alexander Graf wrote:
>> 
>> On 14.03.2013, at 02:53, David Gibson wrote:
>> 
>>> Currently, the pseries machine initializes the cpus, then the XICS
>>> interrupt controller.  However, to support the upcoming in-kernel XICS
>>> implementation we will need to initialize the irq controller before the
>>> vcpus.  This patch makes the necesssary rearrangement.  This means the
>> 
>> We're changing that notion in the in-kernel XICS discussions.  The flow will 
>> look like this:
>> 
>>  * create vcpus
>>  * create XICS
>>  * foreach (vcpu)
>>      * enable_cap(vcpu, CAP_XICS_SERVER, xics_handle)
>> 
>> However, that means we still need to know the maximum number of
>> supported vcpus during the create phase. That number can be bigger
>> than smp_cpus though, since you probably want to support hotplug add
>> of CPUs later on.
>> 
>> Can't we just make the number of supported "interrupt servers" a
>> constant?
> 
> I suppose, but we need an allocation for each one, so its a bit ugly.
> In any case although the comment is a bit out of date, this patch also
> creates a logical place to put per-cpu XICS initialization which we
> will still need for the new interface.

So how would you model CPU hotplug add?


Alex