linux-kernel - Re: Fix built-in early-load Intel microcode alignment

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Message-ID: <CACMCwJLJCA2iXS0QMKKAWQv252oUcmfsNvwDNP5+4Z_9VB-rTg@mail.gmail.com>
Date:   Wed, 15 Jan 2020 20:46:04 +0200
From:   Jari Ruusu <jari.ruusu@...il.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Borislav Petkov <bp@...en8.de>, Fenghua Yu <fenghua.yu@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        johannes.berg@...el.com, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: Fix built-in early-load Intel microcode alignment

On 1/15/20, Luis Chamberlain <mcgrof@...nel.org> wrote:
> On Mon, Jan 13, 2020 at 09:58:25PM +0200, Jari Ruusu wrote:
>> Before that 16-byte alignment patch was applied, my only one
>> microcode built-in BLOB was "accidentally" 16-byte aligned.
>
> How did it accidentially get 16-byte aligned?

Old code aligned it to 8-bytes.
There is 50/50-chance of it also being 16-byte aligned.
So it ended up being both 8-byte and 16-byte aligned.

> Also, how do you *know* something is broken right now?

I haven't spotted brokenness in Linux microcode loader other
than that small alignment issue.

However, I can confirm that there are 2 microcode updates newer
than what my laptop computer's latest BIOS includes. Both newer
ones (20191115 and 20191112) are unstable on my laptop computer
i5-7200U (fam 6 model 142 step 9 pf 0x80). Hard lockups with both
of them. Back to BIOS microcode for now.

-- 
Jari Ruusu  4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD  ACDF F073 3C80 8132 F189