linux-kernel - Re: [PATCH v4 02/11] x86/startup_64: Replace pointer fixups with RIP-relative references

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Message-ID: <CAMj1kXH7CtN2j1os7Ujw7G_xtD2H0g=pfxNBLK=ayj4XGPkudA@mail.gmail.com>
Date: Mon, 19 Feb 2024 11:47:39 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org, 
	Kevin Loughlin <kevinloughlin@...gle.com>, Tom Lendacky <thomas.lendacky@....com>, 
	Dionna Glaze <dionnaglaze@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
	Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>, linux-arch@...r.kernel.org, 
	llvm@...ts.linux.dev
Subject: Re: [PATCH v4 02/11] x86/startup_64: Replace pointer fixups with
 RIP-relative references

On Mon, 19 Feb 2024 at 11:01, Borislav Petkov <bp@...en8.de> wrote:
>
> On Sat, Feb 17, 2024 at 02:58:29PM +0100, Ard Biesheuvel wrote:
> > More testing is always good, but I am not particularly nervous about
> > these changes.
>
> Perhaps but there's a big difference between testing everything as much
> as one can and *then* queueing it - vs testing a bit, not being really
> nervous about the changes and then someone reporting a snafu when the
> patches are already in Linus' tree.
>
> Means dropping everything and getting on that. And then imagine a couple
> more breakages happening in parallel and needing urgent attention.
>
> Not something you wanna deal with. Speaking from my experience, at
> least.
>

Not disagreeing with that.

> > I could split this up into 3+ patches so we could bisect any resulting
> > issues more effectively.
>
> Yeah, splitting changes into separate bits - ala, one logical change per
> patch - is always a good idea.
>
> In this particular case, I don't mind splitting them even more so that
> it is perfectly clear what happens and looking at those changes doesn't
> make people have to go look at the source to figure out what the change
> actually looks like applied, in order to fully grok it.
>

I split this into 5 patches for v5. The final patch in this v4 is
broken for CONFIG_X86_5LEVEL=n so I was going to have to respin
anyway. (I'll pick up the latest version of patch #1 you pasted)