linux-kernel - Re: [PATCH 1/5] Skip timer works.patch

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Date:	Thu, 16 Nov 2006 15:08:40 -0800
From:	Zachary Amsden <zach@...are.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	Rusty Russell <rusty@...tcorp.com.au>, Andi Kleen <ak@....de>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] Skip timer works.patch

Andrew Morton wrote:
> On Thu, 19 Oct 2006 17:09:22 -0700
> Zachary Amsden <zach@...are.com> wrote:
>
>   
>> Add a way to disable the timer IRQ routing check via a boot option.  The
>> VMI timer code uses this to avoid triggering the pester Mingo code, which
>> probes for some very unusual and broken motherboard routings.  It fires
>> 100% of the time when using a paravirtual delay mechanism instead of
>> using a realtime delay, since there is no elapsed real time, and the 4 timer
>> IRQs have not yet been delivered.
>>
>> In addition, it is entirely possible, though improbable, that this bug
>> could surface on real hardware which picks a particularly bad time to enter
>> SMM mode, causing a long latency during one of the timer IRQs.
>>
>> While here, make check_timer be __init.
>>
>>     
>
> Andi seems to have merged this patch but from somewhere I picked up a
> different version, below.
>
> I think the version I have is better.  Because the patch Andi has merged is
> cast in terms of "irq testing", which is broad.  But that's not what the
> patch does - the patch handles only timers.
>
> IOW, this:
>
>   
>> +
>> +	noirqtest	[IA-32,APIC] Disables the code which tests for broken
>> +			timer IRQ sources.
>>     
>
> is misleadingly named.  This:
>
> +       no_timer_check  [IA-32,X86_64,APIC] Disables the code which tests for
> +                       broken timer IRQ sources.
> +
>
> is better, no?
>
> But right now, I'll settle for anything which usually compiles.
>
>   

Yes, the name sucks.  There is no real reason to actually have a boot 
parameter at all once the paravirt / VMI patches are in, but I wanted 
something to be able to set timer_irq_really_works until then to avoid 
someone accidentally removing it.

Zach
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