linux-kernel - RE: [RFC 0/9] mce recovery for Sandy Bridge server

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Date:	Wed, 25 May 2011 09:44:10 -0700
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Huang, Ying" <ying.huang@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: RE: [RFC 0/9] mce recovery for Sandy Bridge server

> How about separating stuffs in:
> step1) Add support for AR in user space :
>   - send sigbus to affected processes, poison affected memory
>   - panic if error is in kernel
> step2) Add support for AR in kernel
>   - some new notify/handle mechanism etc.
>
> It seems too big jump for me.

Agreed - we can go step by step with different recovery cases. Deciding
which to implement is a classic benefit vs. effort trade off.

For each case determine some ball-park numbers for the percentage of
memory that will be in the state you wish to recover (hence user-mode
scores very highly because most people buy machines to run applications,
though there are some exceptions like file servers).

Determine the effort and invasiveness of a solution to recover - here
it is clear that a way to handle arbitrary kernel memory corruption
is never going to fly - but there is hope for some simple cases like
copy to/from user (that already are specially tagged so that user level
page faults can be processed).

-Tony
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