linux-kernel - Re: [PATCH v16 8/8] x86/smpboot: Allow parallel bringup for SEV-ES

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Message-ID: <4dbdd277c4b26ae4b971a910209a3279f79f6837.camel@infradead.org>
Date:   Thu, 23 Mar 2023 09:04:11 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Usama Arif <usama.arif@...edance.com>, tglx@...utronix.de,
        kim.phillips@....com, brgerst@...il.com, piotrgorski@...hyos.org,
        oleksandr@...alenko.name, arjan@...ux.intel.com, mingo@...hat.com,
        dave.hansen@...ux.intel.com, hpa@...or.com, x86@...nel.org,
        pbonzini@...hat.com, paulmck@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rcu@...r.kernel.org, mimoja@...oja.de, hewenliang4@...wei.com,
        thomas.lendacky@....com, seanjc@...gle.com, pmenzel@...gen.mpg.de,
        fam.zheng@...edance.com, punit.agrawal@...edance.com,
        simon.evans@...edance.com, liangma@...ngbit.com,
        gpiccoli@...lia.com, Sabin Rapan <sabrapan@...zon.com>
Subject: Re: [PATCH v16 8/8] x86/smpboot: Allow parallel bringup for SEV-ES

On Thu, 2023-03-23 at 09:51 +0100, Borislav Petkov wrote:
> On Thu, Mar 23, 2023 at 08:32:49AM +0000, David Woodhouse wrote:
> > and maybe find some other stuff to cargo-cult to make it safe to run
> > C code that early...
> 
> I'm trying to have less shit asm, not more if possible. We've been
> aiming to convert stuff to C for years.

Absolutely, I understand. There are a few hoops we have to jump through
to be able to run C code this early, but it's worth it.

> WTF are you calling cargo-cult?

Off the top of my head, I don't actually *remember* all the hoops we
have to jump through to run C code this early.

But there is head64.c with examples. By 'cargo cult' I refer to the
process of copying what they do even if we don't really understand it.

I spotted that it builds with -pg, and that the functions in there are
tagged with __head to put them in the .head.text section. I didn't look
much further; there might be *other* details to copy… to 'cargo cult'.


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