linux-kernel - Re: [PATCH 6/8] SGI x86_64 UV: Limit the number of microcode messages

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Message-ID: <4AE5EA71.2050304@sgi.com>
Date:	Mon, 26 Oct 2009 11:29:05 -0700
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Tigran Aivazian <tigran@...azian.fsnet.co.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jack Steiner <steiner@....com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Andreas Mohr <andi@...as.de>, Hugh Dickins <hugh@...itas.com>,
	Hannes Eder <hannes@...neseder.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/8] SGI x86_64 UV: Limit the number of microcode	messages



Ingo Molnar wrote:
> * Dmitry Adamushko <dmitry.adamushko@...il.com> wrote:
> 
>> 2009/10/24 Tigran Aivazian <tigran@...azian.fsnet.co.uk>:
>>> On Sat, 24 Oct 2009, Dmitry Adamushko wrote:
>>>>> -       printk(KERN_INFO "microcode: CPU%d sig=0x%x, pf=0x%x,
>>>>> revision=0x%x\n",
>>>>> +       if (cpu_num < 4 || !limit_console_output(false))
>>>>> +               printk(KERN_INFO
>>>>> +                       "microcode: CPU%d sig=0x%x, pf=0x%x,
>>>>> revision=0x%x\n",
>>>>>                        cpu_num, csig->sig, csig->pf, csig->rev);
>>>>>
>>>> Hmm, I guess we wouldn't lose a lot by simply removing those messages
>>>> completely. Per-cpu pf/revision is available via /sys anyway.
>>> The reason for printing them is that the pf (possibly others?) can change by the update and so the log has this info handy.
>> We might store the old sig/pf/revision set as well, export them via
>> /sys or/and print them at update-to-new-microcode time.
>>
>> If it's really so useful to have this info in the log and, at the same
>> time, to avoid the flood of messages (which, I guess for the majority
>> of systems, are the same) at startup time, we might delay the printout
>> until the end of microcode_init(). Then do something like this:
>>
>> microcode cpu0: up to date version sig, pf, rev          // let's say,
>> it was updated by BIOS
>> microcode cpus [1 ... 16] : update from sig, pf, rev to sig, pf2, rev2.
>>
>> Anyway, my humble opinion, is that (at the very least) the current
>> patch should be accompanied by a similar version for amd.
> 
> yeah. Since we load new microcode on all cpus it's enough to print it 
> for the boot CPU or so.
> 
> Having the precise microcode version printed (or exposed somewhere in 
> /sys) is useful - sometimes when there's a weird crash in some prototype 
> CPU one of the first questions from hw vendors is 'which precise 
> microcode version was that?'.
> 
> 	Ingo

I would agree especially in the case where not all the cpus are exactly
the same.  But so far, I've only seen variations of the speed of the cpus
not it's generic type, in an SSI.  So the version of the microcode was
identical in all cases.

Thanks,
Mike
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