Re: [Qemu-devel] [RFC PATCH v2.1 11/12] xics, xics_kvm: Handle CPU unplug correctly

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Apr 05, 2016 at 07:24:39PM -0500, Michael Roth wrote:
> Quoting Bharata B Rao (2016-03-31 03:39:20)
> > XICS is setup for each CPU during initialization. Provide a routine
> > to undo the same when CPU is unplugged. While here, move ss->cs management
> > into xics from xics_kvm since there is nothing KVM specific in it.
> > Also ensure xics reset doesn't set irq for CPUs that are already unplugged.
> > 
> > This allows reboot of a VM that has undergone CPU hotplug and unplug
> > to work correctly.
> > 
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/intc/xics.c        | 14 ++++++++++++++
> >  hw/intc/xics_kvm.c    |  8 ++++----
> >  include/hw/ppc/xics.h |  1 +
> >  3 files changed, 19 insertions(+), 4 deletions(-)
> > 
> > diff --git a/hw/intc/xics.c b/hw/intc/xics.c
> > index 213a370..9fdb551 100644
> > --- a/hw/intc/xics.c
> > +++ b/hw/intc/xics.c
> > @@ -45,6 +45,18 @@ static int get_cpu_index_by_dt_id(int cpu_dt_id)
> >      return -1;
> >  }
> > 
> > +void xics_cpu_destroy(XICSState *icp, PowerPCCPU *cpu)
> > +{
> > +    CPUState *cs = CPU(cpu);
> > +    ICPState *ss = &icp->ss[cs->cpu_index];
> > +
> 
> If the following assertion is false, I think you'd get an OOB before you
> reached it due to the assignment above.

It should be ok.  The assignment above will compute an out of bounds
address, but it doesn't dereference it.

> > +    assert(cs->cpu_index < icp->nr_servers);
> > +    assert(cs == ss->cs);
> > +
> > +    ss->output = NULL;
> > +    ss->cs = NULL;
> > +}
> > +
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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