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

[Michael Roth <mdroth@linux.vnet.ibm.com>]

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.

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