linux-kernel - Re: [PATCH] x86/microcode/AMD: check microcode file sanity before loading it

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Message-ID: <20180310164654.GD8261@pd.tnic>
Date:   Sat, 10 Mar 2018 17:46:55 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/microcode/AMD: check microcode file sanity before
 loading it

On Sat, Mar 10, 2018 at 05:16:40PM +0100, Maciej S. Szmigiero wrote:
> To make sure that it is clear what this patch is about:

I know what you're trying to do but it seems you don't want to listen.
So let me try one last time to clear your confusion.

> It *isn't* about verifying the actual microcode update, that is, the
> blob that gets sent to the CPU as the new microcode.
> Such verification is (hopefully) done by the CPU itself.

Yes, it is done by the CPU. Microcode is encrypted.

> There is no container file at all for family 17h (Zen) so
> distributions like OpenSUSE that include this file must have gotten it
> from some other source

Or maybe they've gotten it from AMD directly. Don't you think that
getting microcode from the CPU vendor directly is the logical thing?

> That's why to get things like IBPB it is sometimes necessary to use
> a newer microcode version than included in linux-firmware, sourced for
> example from a BIOS update.

linux-firmware will get F17h microcode soon.

> Since BIOS updates contain only actual (raw) microcode updates one
> has to place it in a microcode container file so this driver can parse
> it.
> 
> As far I know there is no tool to automate this work so one has to
> manually tweak the container metadata.

Let me get this straight: am I reading this correctly that you've tried
to carve out the F17h microcode from a BIOS update blob and you're
trying to load that?!?

If so, you could've simply taken a distro microcode package and used
F17h microcode from there - they are all the same.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.