linux-kernel - RE: [PATCH] x86/MCE: Remove MCP

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Date:   Mon, 7 Nov 2016 17:48:46 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     linux-edac <linux-edac@...r.kernel.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] x86/MCE: Remove MCP_TIMESTAMP

> So, get rid of all that and simply log an MCE with a TSC value always.
> Simplifies the code a bit too.

I'm not necessarily opposed to this ... but there was once some logic behind when
logged TSC, and when we didn't.  Essentially we wanted the TSC when we were
logging from #CMCI or #MC .... because the detection of the error was fresh, and
wanted as much precision on the logged time as possible to compare with logged
errors from other banks/cpus. This might allow us to distinguish multiple errors logged
in the same #CMCI, from errors logged in separate #CMCI a tenth of a second apart.

If we found the error while polling, we didn’t want to provide a false sense of precision.
The error could have been logged up to five minutes previously (or when logging
errors during the initial poll of the banks an arbitrary time in the past).

-Tony