linux-kernel - RE: [PATCH 1/2 v2] x86, mce, severity: extend the the mce

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Date:	Thu, 6 Nov 2014 21:24:01 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Chen Yucong <slaoub@...il.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"aravind.gopalakrishnan@....com" <aravind.gopalakrishnan@....com>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2 v2] x86, mce, severity: extend the the mce_severity

> I'm under the assumption that at all times, when we get a MCE, MCIP will
> be set. For example, mce_gather_info() reads MCG_STATUS before we call
> mce_severity() in do_machine_check().
>
> Or am I missing something?

Architecturally it is true that MCIP will be set when machine check is signaled.
But, sometimes there are bugs. BIOS has a hook to get an SMI to see the
event before the OS sees the machine check - which gives lots of scope for
things to not happen by the book.  If MCIP isn't set correctly, I'd like to get
on and panic quickly - because all sorts of bad things will happen if a nested
machine check happens and isn't caught because MCIP wasn't set in the first
machine check.

-Tony