linux-kernel - Re: [PATCH -v2 6/7] x86, NMI, Add support to notify hardware error with unknown NMI

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Date:	Wed, 29 Sep 2010 16:17:30 +0800
From:	huang ying <huang.ying.caritas@...il.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Huang Ying <ying.huang@...el.com>,
	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH -v2 6/7] x86, NMI, Add support to notify hardware error
 with unknown NMI

On Tue, Sep 28, 2010 at 11:32 PM, Don Zickus <dzickus@...hat.com> wrote:
> On Tue, Sep 28, 2010 at 08:36:12AM +0800, Huang Ying wrote:
>> > I tend to agree with Robert here.  I don't know if there were any 'rules'
>> > to which handlers get directly called versus ones that go through the
>> > die_chain, so I was originally going to let it go.  But if they aren't
>> > any, it does look cleaner to have everything in die_chains.
>>
>> Personally, I think directly call has better readability than
>
> I am confused what type of readability you are looking for?  Can we create
> a sysfs entry to give you that info?

Sorry for my poor English. I mean code readability here. That is,
notifier_chain makes code harder to understand than direct call.

>> notifier_chain in general. Notifier_chain is for:
>>
>> - Call functions in module.
>> - Need to enable/disable (via register/unregister) at run time.
>> - Call functions from low layer to high layer.
>>
>> Otherwise, notifier_chain should be avoid if possible. So I think it is
>> better to keep direct call as much as possible.
>
> But the problem is you have to export all this platform specific stuff to
> traps.c and surround the code with #ifdef's, which start to look ugly.

There is no #ifdef in my final default_do_nmi(), so I think the code
can be cleaned up without converting everything into notifier block. I
think the rule can be: architecture specific thing should go direct
call, while device driver should be turned into notifier block.

> Is there any reason why traps.c should know about MCA/HEST/<other hardware
> errors>?  Shouldn't it be abstracted away?

Yes. The device drivers should be abstracted away, leaving
architectural logic, such as port 0x61 as direct call. We need
notifier chain, but I just suggest reduce its usage if possible.

> Honestly, I would be interested in creating a southbridge driver and
> moving the port 0x61 code there and keeping the default_do_nmi() function
> stupidly simple (just a call to the die_chain and the
> unknown_nmi_error()).

I think the southbridge drivers should go notifier block, but the port
0x61 code is architectural and should be kept in default_do_nmi().

Best Regards,
Huang Ying
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