linux-kernel - Re: [PATCH] x86 (64): make calibrate_APIC

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Date:	Thu, 24 Jul 2008 18:31:51 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Martin Wilck <martin.wilck@...itsu-siemens.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Wichert, Gerhard" <Gerhard.Wichert@...itsu-siemens.com>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>
Subject: Re: [PATCH] x86 (64): make calibrate_APIC_clock() SMI-safe

[Martin Wilck - Thu, Jul 24, 2008 at 03:55:02PM +0200]
> Cyrill Gorcunov wrote:
>
>> yes, it will issue some effects but it's better then stuck there.
>> More over in 'case of SMI flood with current patch you don't get
>> error message printed i think so you better add max iteration
>> counter so user will see on console (or whatever) that he is got
>> problems.
>>                 - Cyrill -
>
> I disagree. If you have a system that generates SMIs in this extreme  
> frequency, you're better off stuck than running on such an unstable  
> system. The user _will_ see messages on the console if this happens.  
> Note that apparently there are few people who have trouble with this. We  
> did see problems, but never had more than 1 SMI disturbing the  
> calibration procedure.
>
> Anyway, here is another patch that defines max iteration counts. I  
> haven't added a "Signed-off:" line, because I prefer the original 
> version.
>
> Martin
>

yes, Martin, it'll be written on console (just forgot it's not interrupt
driven). I've Cc'ed Maciej in previous message so we should better wait
for his opinion I think. For me the almost ideal solution could be like -
lets user to choose what he wants. I mean you even could add some boot
param to specify behaviour on a such case like panic on SMI flood during
calibration. yes - if we got smi flood we have serious troubles anyway but
i don't think that being just stuck is good choise. And that is why I do like
much more _this_ patch. Anyway - thanks!

		- Cyrill -
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