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

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Message-ID: <1516974600.2801.10.camel@redhat.com>
Date:   Fri, 26 Jan 2018 14:50:00 +0100
From:   Petr Oros <poros@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
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

Borislav Petkov píše v Pá 26. 01. 2018 v 12:58 +0100:
> On Fri, Jan 26, 2018 at 12:45:35PM +0100, Petr Oros wrote:
> > During time of facing the Spectre vulnerability and the requirement of handling
> > different microcode updates, it has shown, that it would be useful to have
> > additional information which microcode version was in BIOS, if the early-update
> > routine will apply an update.
> 
> Dmesg tells you if the update was applied or not.
> 
> And if you really wanna know the old microcode revision, you can boot
> with "dis_ucode_ldr" and do "grep microcode /proc/cpuinfo".
> 

Ohh, yes, it is easy and fast. Mainly in time when new microcodes are released
frequently and microcode can be early updated from initrd too.

But what in production? Edit boot params, restart server, grep /proc/cpuinfo and
restart again? Why i can not read it just from dmesg?

Thanks,
-Petr