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

[Greg Kurz]

On Fri, 9 Jun 2017 12:24:52 +1000
David Gibson <address@hidden> wrote:

> On Thu, Jun 08, 2017 at 10:45:30AM +0200, Greg Kurz wrote:
> > On Thu, 8 Jun 2017 12:01:12 +1000
> > David Gibson <address@hidden> wrote:
> >   
> > > On Wed, Jun 07, 2017 at 07:17:09PM +0200, 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.    
> > > 
> > > Ok, what enforces those ordering constraints?
> > >   
> > 
> > I'm not sure about what you're asking... I had to re-order because
> > xics_cpu_setup() used to be called after the vCPU is realized and
> > put in PAPR mode.  
> 
> Duh, sorry, I wasn't thinking to ask about realize order, since that's
> manual and you've re-ordered it to be correct.
> 
> You also mention that reset order matters, and I'm less clear on what
> guarantees that the reset handlers for the components get called in
> the right order.
> 

Oops... my bad, this is a mistake in the changelog. The KVM error I was
seing isn't related to CPU reset as I was thinking first but to
cpu_ppc_set_papr()... :-\

The last sentence should rather be something like:

"We also need to call spapr_cpu_init() before ICPState realization in
 order to enable PAPR mode in KVM."

Can you fix this in your tree or should I send an updated version ?

Cheers,

--
Greg

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