On Fri, Aug 05, 2016 at 08:21:59PM +0530, Bharata B Rao wrote: > On Fri, Aug 05, 2016 at 05:50:29PM +1000, David Gibson wrote: > > Prior to c8721d3 "spapr: Error out when CPU hotplug is attempted on older > > pseries machines", attempting to use query-hotpluggable-cpus on pseries-2.6 > > and earlier machine types would SEGV. > > > > That change fixed that, but due to some unexpected interactions in init > > order and a brown-paper-bag worthy failure to test, it accidentally > > disabled query-hotpluggable-cpus for all pseries machine types, including > > the current one which should allow it. > > > > In fact, query_hotpluggable_cpus needs to be non-NULL when and only when > > the dr_cpu_enabled flag in sPAPRMachineClass is set, which makes > > dr_cpu_enabled itself redundant. > > > > This patch removes dr_cpu_enabled, instead directly setting > > query_hotpluggable_cpus from the machine class_init functions, and using > > that to determine the availability of CPU hotplug when necessary. > > dr_cpu_enabled actually determines if CPU hotplug feature is present > or not. It also controls the creation of DRC-specific properties > in /cpus DT node like ibm,drc-indexes etc > > query_hotpluggable_cpus just tells us if the machine supports the > querying of hotpluggable CPUS. query_hotpluggable_cpus definitely > implies dr_cpu_enabled but dr_cpu_enabled can exist on its own > (theoretically at the least) without query_hotpluggable_cpus.
Um, so that certainly can't happen in practice. Just like
query_hotpluggable_cpus, dr_cpu_enabled is set for pseries-2.7 and no
earlier machine types. There's no way to override it in
configuration.
And even in theory I can't see how dr_cpu_enabled could make any sense
without query_hotpluggable_cpus. The whole hotplug infrastructure is
based around the core objects, which don't exist with the earlier
machine types.
> So I think we should not replace dr_cpu_enabled with query_hotpluggable_cpus.
>
> However, I tested this patch and it works as intended.
>
> Regards,
> Bharata.
>
--
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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