linux-kernel - Re: [PATCH] x86/microcode/intel: print previous microcode revision during early update

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Message-ID: <20180126144918.7jiaezmdhjsiman5@pd.tnic>
Date:   Fri, 26 Jan 2018 15:49:19 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Petr Oros <poros@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/microcode/intel: print previous microcode revision
 during early update

On Fri, Jan 26, 2018 at 02:50:00PM +0100, Petr Oros wrote:
> But what in production? Edit boot params, restart server, grep /proc/cpuinfo and
> restart again? Why i can not read it just from dmesg?

Because you don't need the previous revision.

You only *happen* to need it now but that is being addressed too with
the blacklisting. And when you have broken microcode, it will say:

+               pr_warn("Intel Spectre v2 broken microcode detected; disabling SPEC_CTRL\n");

and if you have microcode which doesn't have IBRS, there won't be
"spec_ctrl" in /proc/cpuinfo.

I don't want people to start paying attention to microcode
revision numbers with the gazillion different revisions and
family/model/steppings out there and the crazy confusion that will ensue
from this.

-- 
Regards/Gruss,
    Boris.

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