linux-kernel - Re: [PATCH 0/2] x86/microcode/amd: Do not overwrite specific patch levels

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Message-ID: <20150710151159.GA761@khazad-dum.debian.net>
Date:	Fri, 10 Jul 2015 12:12:00 -0300
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	Borislav Petkov <bp@...en8.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
	X86 ML <x86@...nel.org>
Subject: Re: [PATCH 0/2] x86/microcode/amd: Do not overwrite specific patch
 levels

On Fri, 10 Jul 2015, Borislav Petkov wrote:
> On Thu, Jul 09, 2015 at 12:03:41PM -0300, Henrique de Moraes Holschuh wrote:
> > Is there any way to notify the user that 'processor microcode updates
> > are not available on this system except through a firmware update' ?
> 
> What for?
> 
> Those microcode patch levels are final and shouldn't be upgraded at all.

Yes, I understand that the operating system is not to attempt to update any
microcode that is listed as 'final'.

However, if that requirement exists because a microcode update applied by
the operating system would interact badly with the current firmware (or
microcode), the user could still get newer microcode (and better features,
errata workarounds, etc) through a full firmware (BIOS/EFI) update.

OTOH, if this is a 'microcode updates newer than the 'final' version exist
only to support changed hardware designs', and thus a board that already
works with 'final' should never need newer microcode, it would be nice to
know that fact.

Anyway, the code does not look like what I would expect if it is the later
case ("updates past 'final' exist only to support for changed hardware
design): it blacklists updates from 'final' to anything else, but it still
allows microcode with a version that is less than 'final' to be updated to
something that is higher than 'final', etc.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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