linux-kernel - Re: [PATCH] x86/microcode: Refactor Intel microcode loading

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Date:   Thu, 4 Apr 2019 18:47:41 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Jann Horn <jannh@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        David Laight <David.Laight@...lab.com>
Subject: Re: [PATCH] x86/microcode: Refactor Intel microcode loading

On Thu, Apr 04, 2019 at 06:31:37PM +0200, Jann Horn wrote:
> Uuuh. I *definitely* tested this. I ran this yesterday evening on my
> home machine, on top of commit
> 14c741de93861749dfb60b4964028541f5c506ca from Linus' tree, plus two
> cherry-picked fixes for drm/ttm. I specifically made sure that I had
> the old microcode version before reloading these ways and I had the
> new version after reloading. And the verbose dmesg logs also looked
> okay.

How did you check the microcode revision before and after? /proc/cpuinfo?

Because that old method doesn't say anything in dmesg if there's no
debugging output, only the iucode_tool says something like the below if
you enable verbose output:

# iucode-tool -v --kernel=/dev/cpu/microcode /lib/firmware/intel-ucode/06-3a-09
iucode-tool: processed 1 valid microcode(s), 1 signature(s), 1 unique signature(s)
iucode-tool: selected 1 microcode(s), 1 signature(s)
iucode-tool: Uploading selected microcodes to: /dev/cpu/microcode
iucode-tool: /dev/cpu/microcode: 1 microcode entries uploaded, 13312 bytes

-- 
Regards/Gruss,
    Boris.

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