Date: Sat, 25 Jan 2014 19:14:09 +0100
From: Andi Kleen <andi@firstfloor.org>
To: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Andi Kleen <andi@firstfloor.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 2/2] x86, microcode: Add option to allow downgrading of
 microcode
Message-ID: <20140125181409.GE20765@two.firstfloor.org>
References: <1390598339-18740-1-git-send-email-andi@firstfloor.org>
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 <20140125163558.GC25531@khazad-dum.debian.net>
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On Sat, Jan 25, 2014 at 02:35:58PM -0200, Henrique de Moraes Holschuh wrote:
> On Fri, 24 Jan 2014, Andi Kleen wrote:
> > For testing purposes it can be useful to downgrade microcode.
> > Normally the driver only allows upgrading.
> 
> The code is not prepared to work correctly when downgrading is allowed, in
> the presence of shadowed microcode.  When a firmware request results in more

As I wrote it's only for testing purposes when you know what you're doing
(typically with a special micro code file)

Your whole argument is irrelevant, as it only applies to normal users
who should never use this option.

> Also, since you're going to mess with this, why don't you implement the
> correct semanthics for microcode with the sign bit set?  Making it signed
> actually makes the current code behaviour worse.
> 
> Refer to: http://lkml.org/lkml/2011/3/21/522

I don't think it makes it worse. In fact I'm essentially implementing
Burt's request "for explicit user action" with the new override option.

Anyways I suppose your rant killed the patch anyways. Congratulations!

-Andi
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