linux-kernel - Builtin microcode does nothing

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Date:	Fri, 20 May 2016 02:55:12 +0200
From:	Gabriel C <nix.or.die@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Builtin microcode does nothing

Hi guys ,

I tested kernel 4.6 with the built in microcode method , following
Documentation/x86/early-microcode.txt.

The kernel config[1] has :

CONFIG_FIRMWARE_IN_KERNEL=y
CONFIG_EXTRA_FIRMWARE="intel-ucode/06-1a-05"
CONFIG_EXTRA_FIRMWARE_DIR="/lib/firmware"

also

CONFIG_MICROCODE=y
CONFIG_MICROCODE_INTEL=y
CONFIG_MICROCODE_AMD=y
CONFIG_MICROCODE_OLD_INTERFACE=y

I also use a basic initrd generated with dracut.

With this kernel the early microcode loading does nothing nor the 'old
interface'.

Interesting is the following :

doing a ' echo 1 >/sys/devices/system/cpu/microcode/reload ' the kernel
finds the buitin firmware and updates the microcode.

...

[  713.273956] platform microcode: firmware: using built-in firmware
intel-ucode/06-1a-05
[  713.274024] microcode: CPU0 sig=0x106a5, pf=0x1, revision=0x15
[  713.274596] microcode: CPU0 updated to revision 0x19, date = 2013-06-21

...

Also the method with the 'combined initrd' works just fine.

[1] http://crazy.dnshome.de/~crazy/lkml/config/config

Please CC me since I'm not subscribed to the list.

Best Regards,

Gabriel C

( sorry but gmail messed up so I resend )