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From: Luis Chamberlain <mcgrof@kernel.org>
To: Jari Ruusu <jari.ruusu@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>, Fenghua Yu <fenghua.yu@intel.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	johannes.berg@intel.com, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org, Hans de Goede <hdegoede@redhat.com>,
	Andy Lutomirski <luto@kernel.org>
Subject: Re: Fix built-in early-load Intel microcode alignment
Date: Wed, 15 Jan 2020 18:58:12 +0000	[thread overview]
Message-ID: <20200115185812.GH11244@42.do-not-panic.com> (raw)
In-Reply-To: <CACMCwJLJCA2iXS0QMKKAWQv252oUcmfsNvwDNP5+4Z_9VB-rTg@mail.gmail.com>

On Wed, Jan 15, 2020 at 08:46:04PM +0200, Jari Ruusu wrote:
> On 1/15/20, Luis Chamberlain <mcgrof@kernel.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.

But *how? Why is there a 50/50 chance of it being aligned to
16 bytes if 8 bytes are currently specified?

> So it ended up being both 8-byte and 16-byte aligned.

What do you mean both? How can it be aligned to both?

> > 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.

I was more interested in how you are *certain*, other than manualcode
inspection, and that a spec indicates we should use 16 bytes for Intel
microcode -- that the 8 byte alignment *does* not allow users to
currently update their Intel CPU microcode for built-in firmware.                                      

From what I gather so far we have no case yet reported where we know for
sure it fails right now with the 8 byte alignment on 64-bit.
										                                                                                
This information would just be useful for the commit log.

  Luis

  reply	other threads:[~2020-01-15 18:58 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-12 13:00 Fix built-in early-load Intel microcode alignment Jari Ruusu
2020-01-12 13:03 ` Jari Ruusu
2020-01-12 14:02   ` Greg KH
2020-01-13  6:30     ` Jari Ruusu
2020-01-13  6:42       ` Greg KH
2020-01-13 15:47 ` Luis Chamberlain
2020-01-13 19:44   ` Linus Torvalds
2020-01-15  2:27     ` Luis Chamberlain
2020-01-18 20:10       ` Bjorn Andersson
2020-01-13 19:58   ` Jari Ruusu
2020-01-13 20:08     ` Borislav Petkov
2020-01-13 20:30       ` Jari Ruusu
2020-01-13 20:46         ` Borislav Petkov
2020-01-15  2:15     ` Luis Chamberlain
2020-01-15 18:46       ` Jari Ruusu
2020-01-15 18:58         ` Luis Chamberlain [this message]
2020-01-15 19:41           ` Linus Torvalds
2020-01-15 19:00         ` Andy Lutomirski
2020-01-15 19:15           ` Jari Ruusu
2020-01-15 19:49             ` Linus Torvalds
2020-01-16  6:55               ` Jari Ruusu
2020-01-16 19:16                 ` Raj, Ashok
2020-01-17  9:47                   ` Jari Ruusu
2020-02-03 20:10 ` Luis Chamberlain

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