Re: [Qemu-ppc] [PATCH v3 3/5] xics: setup cpu at realize time

[Greg Kurz]

On Thu, 8 Jun 2017 11:53:29 +1000
David Gibson <address@hidden> wrote:

> On Wed, Jun 07, 2017 at 10:55:07PM +0200, Greg Kurz wrote:
> > On Wed, 7 Jun 2017 20:11:38 +0200
> > Cédric Le Goater <address@hidden> wrote:
> >   
> > > On 06/07/2017 07:17 PM, Greg Kurz wrote:  
> > > > Until recently, spapr used to allocate ICPState objects for the lifetime
> > > > of the machine. They would only be associated to vCPUs in 
> > > > xics_cpu_setup()
> > > > when plugging a CPU core.
> > > > 
> > > > Now that ICPState objects have the same lifecycle as vCPUs, it is
> > > > possible to associate them during realization.
> > > > 
> > > > This patch hence open-codes xics_cpu_setup() in icp_realize(). The vCPU
> > > > is passed as a property. Note that vCPU now needs to be realized first
> > > > for the IRQs to be allocated. It also needs to resetted before ICPState
> > > > realization in order to synchronize with KVM.
> > > > 
> > > > Since ICPState objects are freed when unrealized, xics_cpu_destroy() 
> > > > isn't
> > > > needed anymore and can be safely dropped.    
> > > 
> > > I like the idea but I think the assignment of ->cs attribute should be 
> > > moved under icp_kvm_cpu_setup(), as it is only used under xics_kvm by 
> > > the kvm_vcpu_ioctl() calls. 
> > >   
> > 
> > Well, cs->cpu_index is also used for traces and to implement the 'info pic'
> > monitor command.  
> 
> Right.  I think it makes sense for the ICP to have a handle on it's
> associated CPU, even if we don't actually use it in all cases right
> now.  So I have no problem with the property being in all ICPs; I
> think that will be cleaner than special casing xics_kvm.  Especially
> if we have to un-special-case it sometime in future because we need
> to access the CPU object for some reason we haven't thought of yet.
> 

We had discussed with Cedric about that actually but when I started
to write code, I had the impression that I would have to do convoluted
things to get rid of the CPU handle in ICP.

Thanks for confirming this.

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