From: Chris Brannon <cmb@prgmr.com>
To: alpine-user@lists.alpinelinux.org
Subject: Re: Syslinux & Xen & microcode updates
References: <alpine.DEB.2.21.99999.352.1910210236100.13135@trent.utfs.org>
	<87r236t8cl.fsf@cmbmachine.messageid.invalid>
	<alpine.DEB.2.21.99999.352.1910211025010.13135@trent.utfs.org>
Date: Mon, 21 Oct 2019 11:29:02 -0700
In-Reply-To: <alpine.DEB.2.21.99999.352.1910211025010.13135@trent.utfs.org>
	(Christian Kujau's message of "Mon, 21 Oct 2019 10:45:00 -0700 (PDT)")
Message-ID: <875zkit0k1.fsf@cmbmachine.messageid.invalid>
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Christian Kujau <lists@nerdbynature.de> writes:

> That didn't work, as vmlinuz-vanilla now tried to find its initrd in 
> intel-ucode.img, but that did not contain a rootfs and it panicked with 
> this infamous "Kernel panic - not syncing: VFS: Unable to mount root 
> fs..." message.

I'm sorry, I gave you the wrong order, and I forgot that order is
very important here.  The order
--- initramfs-vanilla --- intel-ucode.bin
would have worked, if you need to keep them un-concatenated for some reason.

> So, while "intel-ucode.img --- initramfs-vanilla" did not work (tested 
> just now), I fiddled around some more (boy, was it late last night) and 
> although I dismissed it first, the concatenation of the microcode and the 
> initrd[0] did indeed work, although I am missing the usual "microcode" 
> messages in dmesg, something like:
>
>   microcode: sig=0x806e9, pf=0x80, revision=0xb4
>   microcode: Microcode Update Driver: v2.2.

I would expect this, because the microcode is now loaded by Xen before
Linux boots.  Linux sees the processor with up-to-date microcode.

Try `sudo xl dmesg |grep -i microcode` to verify that Xen is loading it.

You can also get the revision number for your processor's microcode from
/proc/cpuinfo: `grep -i microcode /proc/cpuinfo`.

If you have a copy of the GenuineIntel.bin file extracted from
intel-ucode.img, you could compare the revision number from
/proc/cpuinfo against the output of a command like:
iucode_tool  --list GenuineIntel.bin |grep -E 'sig 0x000806e9'
Look for "rev 0x" and some hex digits.  iucode_tool's output pads with
0s, /proc/cpuinfo doesn't.

Probably Alpine's update-extlinux needs some support added for the combo
of Xen and microcode.

-- Chris