linux-kernel - Re: [PATCH] x86/acpi: Remove indirect jump from wakeup

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Message-ID: <CAMj1kXF7n_uREtOnWJsXETRPtZ-rMrt6vp0a1DwJK+zuDJbTgQ@mail.gmail.com>
Date: Sun, 18 Jan 2026 21:51:18 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Brian Gerst <brgerst@...il.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, 
	Ingo Molnar <mingo@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Borislav Petkov <bp@...en8.de>, "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] x86/acpi: Remove indirect jump from wakeup_long64()

On Sun, 18 Jan 2026 at 20:17, Brian Gerst <brgerst@...il.com> wrote:
>
> On Sun, Jan 18, 2026 at 1:09 PM Ard Biesheuvel <ardb@...nel.org> wrote:
> >
> > On Sun, 18 Jan 2026 at 18:05, Brian Gerst <brgerst@...il.com> wrote:
> > >
> > > wakeup_long64() is called from common_startup_64() via inital_code, so
> >
> > initial_code
> >
> > > it is already running on the normal virtual mapping.  There is no need
> > > to use an indirect jump since it is not switching mappings.
> > >
> >
> > By the same reasoning (i.e., that everything executes in the kernel
> > virtual mapping) you might also convert the movq on line 55 into a
> > RIP-relative leaq, as it is the only remaining non-RIP relative access
> > in the file. That way, I can drop this file from my PIE series too.
>
> This is more of a general cleanup than specifically for PIE.  When
> resume was converted to using the SMP trampoline, a lot of the old
> cruft was left in place and I am working on additional cleanups.

Fair enough.