On Thu, Jul 21, 2016 at 05:54:36PM +0200, Igor Mammedov wrote: > It will enshure that cpu_index for a given cpu stays the same > regardless of the order cpus has been created/deleted. > > No compat code is needed as for initial cpus index in > possible_cpus[] matches cpu_index that's been auto-allocated > in cpu_exec_init(). > > Tha same applies for hotplug with cpu-add command if cpus are > added sequentially in increasing order as 'id' matches cpu_index. > > If cpu-add had been used for creating out-of-order cpus, > that created unmigratable instance since it were not possible > to start target with the same cpu_index using old way > of migrating instance with hotplugged cpus: > > * source QEMU with CLI (-smp 1,maxcpus=3 and cpu-add id=2) > following set of cpu_index is allocated [0, 1] with > apics set [0, 2] respectivelly > * target QEMU is started with CLI -smp 2,maxcpus=3 > resulting in set of cpu_index [0, 1] but with > set of apics [0, 1] wich doesn't match source. > > So we don't need compat code in this case as it's never worked > and newelly added device_add support would use stable cpu_index > set by machine to begin with, so it won't have above limitation > and source QEMU could be migrated to destination regardless > of the order cpus were created. > > Signed-off-by: Igor Mammedov <imamm...@redhat.com>
Reviewed-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> hw/i386/pc.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index ac7a4d5..316fb43 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1872,6 +1872,7 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
> DeviceState *dev, Error **errp)
> {
> int idx;
> + CPUState *cs;
> CPUArchId *cpu_slot;
> X86CPUTopoInfo topo;
> X86CPU *cpu = X86_CPU(dev);
> @@ -1972,6 +1973,9 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
> return;
> }
> cpu->thread_id = topo.smt_id;
> +
> + cs = CPU(cpu);
> + cs->cpu_index = idx;
> }
>
> static void pc_machine_device_pre_plug_cb(HotplugHandler *hotplug_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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