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

From: Ard Biesheuvel <ardb@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Ard Biesheuvel <ardb+git@google.com>,
	linux-kernel@vger.kernel.org,
	 Kevin Loughlin <kevinloughlin@google.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	 Dionna Glaze <dionnaglaze@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	 Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	 Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Nathan Chancellor <nathan@kernel.org>,
	 Nick Desaulniers <ndesaulniers@google.com>,
	Justin Stitt <justinstitt@google.com>,
	 Kees Cook <keescook@chromium.org>,
	Brian Gerst <brgerst@gmail.com>,
	linux-arch@vger.kernel.org,  llvm@lists.linux.dev
Subject: Re: [PATCH v4 02/11] x86/startup_64: Replace pointer fixups with RIP-relative references
Date: Mon, 19 Feb 2024 11:47:39 +0100	[thread overview]
Message-ID: <CAMj1kXH7CtN2j1os7Ujw7G_xtD2H0g=pfxNBLK=ayj4XGPkudA@mail.gmail.com> (raw)
In-Reply-To: <20240219100124.GCZdMm9IAWoMcfEKhF@fat_crate.local>

On Mon, 19 Feb 2024 at 11:01, Borislav Petkov <bp@alien8.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)