linux-kernel - AMD EPYC microcode update bug?

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Date:   Tue, 9 Jan 2018 23:28:50 +0100
From:   Gabriel C <nix.or.die@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Borislav Petkov <bp@...en8.de>
Subject: AMD EPYC microcode update bug?

Hello ,

I'm testing an EPYC system right now with 2 EPYC 7281 16-Core Processors.

I'm on 4.15.0-rc7 and tested an update to microcode_amd_fam17h.bin.

First run was made by using the early microcode option with dracut[1]
so loading from a initrd. the driver reported 63 updated CPUs while CPU0
got still old microcode.

snip

 crazy@ant:~/fw$ dmesg | grep microcode
[    2.615876] microcode: microcode updated early to new patch_level=0x08001213
[    2.615906] microcode: CPU0: patch_level=0x08001207
[    2.615920] microcode: CPU1: patch_level=0x08001213

...

crazy@ant:~/fw$ cat /proc/cpuinfo | head -n 30
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 23
model           : 1
model name      : AMD EPYC 7281 16-Core Processor
stepping        : 2
microcode       : 0x8001207

....

After reloading the microcode with

echo 1 >  /sys/devices/system/cpu/microcode/reload

CPU0 got new microcode too.

Now I tested the same but without initrd early microcode loading
and CONFIG_EXTRA_FIRMWARE set like this:

CONFIG_EXTRA_FIRMWARE="amd-ucode/microcode_amd.bin
amd-ucode/microcode_amd_fam15h.bin amd-ucode/microcode_amd_fam16h.bin
amd-ucode/microcode_amd_fam17h.bin"

This time all CPUs got update fine without the need of reloading the microcode.

Is that some sort timing problem ?

Also I notice on a Intel system the 'early updating' means that , is
the first I see on dmesg
while on AMD system it seems to fire up much later. Why is that ?

Regards,

Gabriel C

1. Fix for Fam17 micrcode :
 https://github.com/dracutdevs/dracut/commit/19453dc8744e6a59725c43b61b2e3db01cb4c57c#diff-bf0c6db1d4aaaa22a88b2649ddbfcd2a