Re: [PATCH 3/5] intel_idle: Split up and provide per CPU initialization func

[Thomas Renninger <trenn@suse.de>]

On Tuesday, January 17, 2012 02:26:40 PM Thomas Renninger wrote:
> On Tuesday, January 17, 2012 12:06:19 PM Len Brown wrote:
> > On 11/17/2011 05:36 PM, Thomas Renninger wrote:
> > 
> > > Function split up, should have no functional change
> > 
> > benefit?
> The idea was:
> Provide a basic init func which can be called in ACPI CPU hotplug
> context safely before the CPU is brought up the first time and:
> struct cpuinfo_x86
> (like CPU features) of the new CPU is not set up yet.
> Do the idle/throttling/... init later when the physically hotplugged
> CPU is onlined the first time (and therefore got fully booted
> and initialized).
> 
> While I had this working, I now have a better idea which does
> not need this split:
Wait, this cannot work.
A cpu core must/should be online to get cpuidle initialized correctly.

> When the ACPI CPU hotplug event is caught, fill up cpu_data(new_cpu)
> data as much and good as possilbe, do something like:
> memcpy(&cpu_data(new_cpu), &boot_cpu_data, sizeof(struct cpuinfo_x86);
> and adjust:
> phys_proc_id
> cpu_core_id
> apicid
> initial_apicid
> ...
> Then cpuidle (and throttling,...) can be initialized without the need
> of booting up the CPU first.
> 
> Not sure whether the memcpy would succeed if the CPU is not (and never
> was) online. From what I saw it should work, but I am not sure.
> Tejun: Do you know that?
Never mind. If I think it really could make sense, I better post an
example code snippet what I'd like to achieve.

   Thomas