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

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Message-ID: <20200112140218.GA902610@kroah.com>
Date:   Sun, 12 Jan 2020 15:02:18 +0100
From:   Greg KH <greg@...ah.com>
To:     Jari Ruusu <jari.ruusu@...il.com>
Cc:     Borislav Petkov <bp@...en8.de>, Fenghua Yu <fenghua.yu@...el.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: Fix built-in early-load Intel microcode alignment

On Sun, Jan 12, 2020 at 03:03:44PM +0200, Jari Ruusu wrote:
> On 1/12/20, Jari Ruusu <jari.ruusu@...il.com> wrote:
> > Intel Software Developer's Manual, volume 3, chapter 9.11.6 says:
> > "Note that the microcode update must be aligned on a 16-byte
> > boundary and the size of the microcode update must be 1-KByte
> > granular"
> >
> > When early-load Intel microcode is loaded from initramfs,
> > userspace tool 'iucode_tool' has already 16-byte aligned those
> > microcode bits in that initramfs image. Image that was created
> > something like this:
> >
> >  iucode_tool --write-earlyfw=FOO.cpio microcode-files...
> >
> > However, when early-load Intel microcode is loaded from built-in
> > firmware BLOB using CONFIG_EXTRA_FIRMWARE= kernel config option,
> > that 16-byte alignment is not guaranteed.
> >
> > Fix this by forcing all built-in firmware BLOBs to 16-byte
> > alignment.
> 
> Backport of "Fix built-in early-load Intel microcode alignment"
> for linux-4.19 and older stable kernels.

Any hint as to what that git commit id is?

thanks,

greg k-h