linux-kernel - Re: [RFC PATCH 09/11] x86/microcode: Expose EUPDATESVN procedure via sysfs

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Message-ID: <YijMZTc49m/OXRKg@zn.tnic>
Date:   Wed, 9 Mar 2022 16:48:53 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Cathy Zhang <cathy.zhang@...el.com>, linux-sgx@...r.kernel.org,
        x86@...nel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 09/11] x86/microcode: Expose EUPDATESVN procedure via
 sysfs

On Wed, Mar 09, 2022 at 07:42:21AM -0800, Dave Hansen wrote:
> There's a little bit in the cover letter that _implies_ why EUPDATESVN
> isn't called during the actual microcode update:
> 
> > This series implements the infrastructure needed to track and tear
> > down bare-metal enclaves and then run EUPDATESVN. This is expected
> > to be triggered by administrators via sysfs at some convenient time
> > after a microcode update, probably by the microcode update tooling
> > itself.
> 
> This allows the (non-destructive) ucode update and the destructive
> EUPDATESVN procedure to happen at different times.

Which means, that this has even less to do with the microcode loader.
That whole glue can be somewhere in arch/x86/...sgx/ land and be
completely independent.

> If we just want to make the ucode update itself call EUPDATESVN via
> microcode_check(), that makes the ucode update itself destructive to SGX
> enclaves.  That's not the end of the world, but this series is going to
> some amount of trouble (including new ABI) to avoid it.
> 
> Perhaps we need to hear more about why this is so much of an issue.

Yah, it all sounds weird.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette