linux-kernel - Re: [PATCH v8 1/3] x86: Expand exception table to allow new handling options

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Message-ID: <CA+8MBbLm27dmtE-njyYUdLX8LVv91O7g34NG9oLy8n04RaqkCg@mail.gmail.com>
Date:	Sat, 9 Jan 2016 09:45:49 -0800
From:	Tony Luck <tony.luck@...il.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Robert <elliott@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	linux-nvdimm <linux-nvdimm@...1.01.org>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH v8 1/3] x86: Expand exception table to allow new handling options

On Fri, Jan 8, 2016 at 5:52 PM, Andy Lutomirski <luto@...capital.net> wrote:
> Also, I think it would be nicer if the machine check code would invoke
> the handler regardless of which handler (or class) is selected.  Then
> the handlers that don't want to handle #MC can just reject them.

The machine check code is currently a two pass process.

First we scan all the machine check banks (on all processors
at the moment because machine checks are broadcast). We
assess the severity of all errors found.

Then we take action. Panic if the most severe error was fatal,
recover if not.

This patch series tweaks the severity calculation. In-kernel
errors at IPs with a EXTABLE_CLASS_FAULT handler are
now ranked as recoverable. All other kernel errors remain
fatal.

I don't think it is right to unconditionally execute the fix code in the
severity assessment phase.

Perhaps later we can revisit the two pass process?

-Tony