Latest F-21 updates cause non-booting system on some Haswel systems + workaround

[Josh Boyer]

On Fri, Sep 26, 2014 at 2:53 PM, Andrew Lutomirski <luto at mit.edu> wrote:
> On Fri, Sep 26, 2014 at 11:37 AM, Hans de Goede <hdegoede at redhat.com> wrote:
>> Hi All,
>>
>> Just spend some time debugging this and thought I should share this, see:
>>
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=762195
>>
>> for details, I've filed a bug to track fixing this in Fedora:
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=1147062
>>
>> There are 2 ways this problem shows itself:
>>
>> 1) If using an initrd which has been generated with the troublesome microcode
>> update into it, things may already crash during the initrd, e.g. in my case
>> some luks volumes would not unlock because of this
>>
>> 2) When booting an older kernel (and thus an older initrd) things start crashing
>> (mostly systemd* processes, grinding everything to a halt) as soon as udev
>> from the rootfs loads the microcode update
>>
>> 2. often will still get you to an emergency shell, at which point one can
>> create a /etc/modprobe.conf.d/no_microcode.conf file with:
>>
>> blacklist microcode
>>
>> In there to work around the problem, then regenerate the initrds for newer
>> kernels, and you should be good to go until bug 1147062 gets fixed properly.
>
> Yeah, sorry, I should have tried to notify the right Fedora people in advance.

I knew about it.  This is basically a breakdown in communication
between the kernel people and the microcode_ctl owner.  it was
compounded by the fact that I didn't realize our main dracut
maintainer was on PTO so I didn't fix dracut myself until this
morning.

> This is a nasty issue, and no one knows how to solve it for real yet.
> See this long thread:
>
> http://thread.gmane.org/gmane.linux.kernel/1790211

Yeah.  FWIW, I just filed an update to have Fedora use early microcode
by default.  A COPR of this was tested successfully by a few people
that had the Haswell issue.

https://admin.fedoraproject.org/updates/dracut-038-29.git20140903.fc21,kernel-3.16.3-302.fc21

josh