linux-kernel - Re: [PATCH -v3.2 3/3] x86, AMD: Move BSP code to cpu

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Message-ID: <4E3C7520.1060808@zytor.com>
Date:	Fri, 05 Aug 2011 15:56:32 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	"Przywara, Andre" <Andre.Przywara@....com>,
	"Pohlack, Martin" <Martin.Pohlack@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v3.2 3/3] x86, AMD: Move BSP code to cpu_dev helper

On 08/05/2011 03:52 PM, Borislav Petkov wrote:
> On Fri, Aug 05, 2011 at 04:07:40PM -0400, H. Peter Anvin wrote:
>> On 08/05/2011 11:04 AM, Borislav Petkov wrote:
>>> Move code which is run once on the BSP during boot into the cpu_dev
>>> helper.
>>> +static void __cpuinit bsp_init_amd(struct cpuinfo_x86 *c)
>>> +{
>>> +	if (static_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
>>> +
>>
>> You can't use static_cpu_has() here, since this code runs before
>> alternatives -- it will always be false.  Furthermore, for code that
>> only runs once, it is never a win to do patching.
> 
> Oh crap, this is a leftover from when run_on_bsp was struct
> x86_cpuinit_ops member with no args. And I f*cked it up even then
> although I went and got myself a pointer to boot_cpu_data:
> 

I fixed it up directly.

> 
>> Arguably bsp_init should be __init and not __cpuinit, but I don't know
>> how to make that work with the machinery, and is something that can be
>> fixed anyway.
> 
> Yeah, how do we do that? struct cpu_dev is __cpuinitconst,
> x86_cpuinit_ops is __cpuinitdata.
> 
> We could add it to identify_boot_cpu() - there's already some per-vendor
> stuff like init_amd_e400_c1e_mask() which wouldn't hurt to be behind a
> vendor check. early_identify_cpu() does already the vendor check with
> get_cpu_vendor() so later, in identify_cpu() we could add a run_on_bsp()
> which is __init and switch/case on the ->x86_vendor inside.
> 
> Then we can collect all the run-once-on-the-BSP code in there.
> 
> Hmmm..
> 

As I said, we can fix this up incrementally.

	-hpa
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