On Tue, Feb 23, 2016 at 03:10:26PM +0530, Bharata B Rao wrote: > On Tue, Feb 23, 2016 at 04:24:31PM +1100, David Gibson wrote: > > Hi Andreas, > > > > I've now found (with Thomas' help) your RFC series for socket/core > > based cpu hotplug on x86 > > (https://github.com/afaerber/qemu-cpu/compare/qom-cpu-x86). It seems > > sensible enough as far as it goes, but doesn't seem to address a bunch > > of the things that I was attempting to do with the cpu-package > > proposal - and which we absolutely need for cpu hotplug on Power. > > > > 1) What interface do you envisage beyond cpu_add? > > > > The patches I see just construct extra socket and core objects, but > > still control hotplug (for x86) through the cpu_add interface. That > > interface is absolutely unusable on Power, since it operates on a > > per-thread basis, whereas the PAPR guest<->host interfaces can only > > communicate information at a per-core granularity. > > > > 2) When hotplugging at core or socket granularity, where would the > > code to construct the individual thread objects sit? > > > > Your series has the construction done in both the machine init path > > and the hotplug path. The latter works because hotplug occurs at > > thread granularity. If we're hotplugging at core or socket > > granularity what would do the construct? The core/socket object > > itself (in instance_init? in realize?); the hotplug handler? > > something else? > > > > 3) How does the management layer determine what is pluggable? > > > > Both the number of pluggable slots, and what it will need to do to > > populate them. > > > > 4) How do we enforce that toplogies illegal for the platform can't be > > constructed? > > 5) QOM-links > > Andreas, You have often talked about setting up links from machine object > to the CPU objects. Would the below code correctly capture that idea of > yours ? > > #define SPAPR_MACHINE_CPU_CORE_PROP "core" > > /* MachineClass.init for sPAPR */ > static void ppc_spapr_init(MachineState *machine) > { > sPAPRMachineState *spapr = SPAPR_MACHINE(machine); > int spapr_smp_cores = smp_cpus / smp_threads; > int spapr_max_cores = max_cpus / smp_threads; > > ... > for (i = 0; i < spapr_max_cores; i++) { > Object *obj = object_new(TYPE_SPAPR_CPU_CORE); > sPAPRCPUCore *core = SPAPR_CPU_CORE(obj); > char name[32]; > > snprintf(name, sizeof(name), "%s[%d]", SPAPR_MACHINE_CPU_CORE_PROP, > i); > > /* > * Create links from machine objects to all possible cores. > */ > object_property_add_link(OBJECT(spapr), name, TYPE_SPAPR_CPU_CORE, > (Object **)&spapr->core[i], > NULL, NULL, &error_abort); > > /* > * Set the QOM link from machine object to core object for all > * boot time CPUs specified with -smp. For rest of the hotpluggable > * cores this is done from the core hotplug path. > */ > if (i < spapr_smp_cores) { > object_property_set_link(OBJECT(spapr), OBJECT(core), > SPAPR_MACHINE_CPU_CORE_PROP, > &error_abort);
I hope we can at least have a helper function to both construct the
core and create the links, if we can't handle the link creation in the
core object itself.
Having to open-code it in each machine sounds like a recipe for subtle
differences in presentation between platforms, which is exactly what
we want to avoid.
> }
> ...
> }
>
--
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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