linux-kernel - Re: [PATCH v2 2/2] mce: acpi/apei: Add a boot option to disable ff mode for corrected errors

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Date:	Wed, 19 Jun 2013 20:36:40 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
	"ananth@...ibm.com" <ananth@...ibm.com>,
	"masbock@...ux.vnet.ibm.com" <masbock@...ux.vnet.ibm.com>,
	"lcm@...ux.vnet.ibm.com" <lcm@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>
Subject: Re: [PATCH v2 2/2] mce: acpi/apei: Add a boot option to disable ff
 mode for corrected errors

On Wed, Jun 19, 2013 at 06:19:25PM +0000, Luck, Tony wrote:
> > Interesting, why? Why would we even need such an option? My impression
> > is, if ACPI tells us FF, MCE code doesn't poll those banks anymore. So
> > where do the duplicated reports come from?
> 
> The option is only disabling the Linux side of firmware first ... the BIOS
> will still be doing it and generating records to feed to the OS using APEI.
> 
> So Linux may see the error in a bank and report it, and BIOS may report
> the same error.  Though I'd expect that to be rare as whoever saw it first
> would most likely clear the bank before the other could see it.
> 
> I asked for the option because I'm nervous about just skipping some banks
> on the say-so of the BIOS ... what if the BIOS did something wrong. This
> option gives us a way to return to the way things were before this patch.

Yeah, the code I saw only disables the banks in the HEST:

	mce_disable_ce_bank(mc_bank->bank_number)

and leaving the rest in poll mode. But I agree, we need this as a
fallback if BIOS is doing other crack smoking exercises and thus we want
to ignore FF completely.

> These parts are now looking good ... but we still need to tackle what
> Linux does when it does get the CPER record. I suspect we need to
> preserve the existing "fake an mcelog entry with just the address" on
> old platforms, but need to do something smarter on new ones.

Why, fill out struct mce and do mce_log(mce) does not suffice?

I'll take a look at the rest of the stuff tomorrow, on a clear head.

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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