Re: [PATCH for-6.0 3/9] spapr: Fix pre-2.10 dummy ICP hack

[David Gibson]

On Sat, Nov 21, 2020 at 12:42:02AM +0100, Greg Kurz wrote:
> This hack registers dummy VMState entries of ICPs in order to
> support migration of old pseries machine types that used to
> create all smp.max_cpus possible ICPs at machine init.
> 
> Part of the work is to unregister the dummy entries when plugging
> an actual vCPU core, and to register them back when unplugging the
> core. The code that unregisters the dummy ICPs in spapr_core_plug()
> is misplaced: if ppc_set_compat() fails afterwards, the hotplug
> operation will be cancelled and the dummy ICPs won't be registered
> back since the unplug handler isn't called.
> 
> Unregister the dummy ICPs at the end of spapr_core_plug().
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>

Applied to ppc-for-6.0, thanks.

> ---
> 
> The next patch makes this patch a bit useless. I post it
> anyway for the records because it is a programming error.
> ---
>  hw/ppc/spapr.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 394d28d9e081..f58f77389e8e 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -3785,13 +3785,6 @@ static void spapr_core_plug(HotplugHandler 
> *hotplug_dev, DeviceState *dev,
>  
>      core_slot->cpu = OBJECT(dev);
>  
> -    if (smc->pre_2_10_has_unused_icps) {
> -        for (i = 0; i < cc->nr_threads; i++) {
> -            cs = CPU(core->threads[i]);
> -            pre_2_10_vmstate_unregister_dummy_icp(cs->cpu_index);
> -        }
> -    }
> -
>      /*
>       * Set compatibility mode to match the boot CPU, which was either set
>       * by the machine reset code or by CAS.
> @@ -3805,6 +3798,13 @@ static void spapr_core_plug(HotplugHandler 
> *hotplug_dev, DeviceState *dev,
>              }
>          }
>      }
> +
> +    if (smc->pre_2_10_has_unused_icps) {
> +        for (i = 0; i < cc->nr_threads; i++) {
> +            cs = CPU(core->threads[i]);
> +            pre_2_10_vmstate_unregister_dummy_icp(cs->cpu_index);
> +        }
> +    }
>  }
>  
>  static void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState 
> *dev,

-- 
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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