linux-kernel - Problem with late AMD microcode reload/feedback

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Message-ID: <CACna6ryhfaOFS4qjZoLjJqcu5LQd05_jDndL5+GpADTHhu3_7Q@mail.gmail.com>
Date:   Sun, 16 Dec 2018 00:46:05 +0100
From:   Rafał Miłecki <zajec5@...il.com>
To:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Problem with late AMD microcode reload/feedback

Hi,

I'm trying to reload AMD Ryzen Mobile (fam17h) microcode doing:
echo 1 > /sys/devices/system/cpu/microcode/reload

The problem is I don't get any feedback. No error for the "echo"
command, no a single new line in the "dmesg". I have no idea if
microcode has been reloaded or not.

I did a quick pr_info based debugging and I noticed that:
1) load_microcode_amd() calls __load_microcode_amd() and gets UCODE_OK
2) load_microcode_amd() calls find_patch(0) and gets a NULL

because of that NULL load_microcode_amd() doesn't return UCODE_NEW.

Seeing above I've decided to debug find_patch(). It seems to be
calling __find_equiv_id(0) which returns 0.

The last step was debugging __find_equiv_id() and find_equiv_id(). It
seems that find_equiv_id() gets sig 8458000 that doesn't exists in the
equiv_cpu_table:
[19.736770] microcode: [find_equiv_id] sig:8458000
[19.736772] microcode: [find_equiv_id] equiv_table->installed_cpu:8392466
[19.736775] microcode: [find_equiv_id] equiv_table->installed_cpu:8392578

Has my microcode been updated? Is there a way to improve that
microcode loading code? Is find_patch(0) returning a NULL expected or
maybe a bug?

-- 
Rafał