linux-kernel - Re: [PATCH 00/10] x86, xsave: some code cleanups and reworks

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Message-ID: <20100720201740.GE6227@lenovo>
Date:	Wed, 21 Jul 2010 00:17:40 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Robert Richter <robert.richter@....com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/10] x86, xsave: some code cleanups and reworks

On Wed, Jul 21, 2010 at 12:07:29AM +0400, Cyrill Gorcunov wrote:
...
> > 
> > But first question is, is it always !smp_processor_id()? At least
> > current implementation indicates this:
> > 
> 
> I guess so, since it's assigned from boot_cpu_id iirc
> 

well, not true, this id is being set in setup_per_cpu_areas()
note the snippet

		if (cpu == boot_cpu_id)
			switch_to_new_gdt(cpu);

but cycle of assignment is done over all possible cpus so
smp_processor_id will be = 0 for BP but definitely it's
confusing and better to check for BP via explicit cpu == boot_cpu_id
I think. Though I might be missing something.

> >  void __cpuinit identify_secondary_cpu(struct cpuinfo_x86 *c)
> >  {
> >  	BUG_ON(c == &boot_cpu_data);
> >  	...
> > 
> > with:
> > 
> >  #define boot_cpu_data cpu_data[0]
> > 
> > ... which is valid for 32 and 64 bit.
> >
 
	-- Cyrill
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