linux-kernel - Re: [External] [PATCH v2 0/5] x86-64: Remove global variables from boot

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Date:   Fri, 24 Feb 2023 16:38:41 -0500
From:   Brian Gerst <brgerst@...il.com>
To:     Usama Arif <usama.arif@...edance.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        David Woodhouse <dwmw2@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [External] [PATCH v2 0/5] x86-64: Remove global variables from boot

On Fri, Feb 24, 2023 at 3:40 PM Usama Arif <usama.arif@...edance.com> wrote:
>
>
>
> On 24/02/2023 15:42, Brian Gerst wrote:
> > This is based on the parallel boot v11 series.
> >
> > Remove the global variables initial_gs, initial_stack, and
> > early_gdt_descr from the 64-bit boot code.  The stack, GDT, and GSBASE
> > can be determined from the CPU number.
> >
> > v2: - Dropped first two patches which were merged into another patch in
> >        the parallel boot series.
> >      - Fixed a compile error in patch 1 found by the kernel test robot.
> >      - Split out the removal of STARTUP_SECONDARY into a separate patch
> >        and renumber the remaining flags.
> >
> > Brian Gerst (5):
> >    x86/smpboot: Remove initial_stack on 64-bit
> >    x86/smpboot: Remove early_gdt_descr on 64-bit
> >    x86/smpboot: Remove initial_gs
> >    x86/smpboot: Simplify boot CPU setup
> >    x86/smpboot: Remove STARTUP_SECONDARY
> >
> >   arch/x86/include/asm/processor.h |  6 +-
> >   arch/x86/include/asm/realmode.h  |  1 -
> >   arch/x86/include/asm/smp.h       |  5 +-
> >   arch/x86/kernel/acpi/sleep.c     |  5 +-
> >   arch/x86/kernel/head_64.S        | 99 ++++++++++++--------------------
> >   arch/x86/kernel/smpboot.c        |  6 +-
> >   arch/x86/xen/xen-head.S          |  2 +-
> >   7 files changed, 49 insertions(+), 75 deletions(-)
> >
>
> Its weird putting something in earlier patches like
> STARTUP_APICID_CPUID_*,STARTUP_SECONDARY.. and removing/changing it
> later on in *the same series*. Maybe better to keep this as a separate
> series from parallel smp? i.e. not include this in v12 and review it
> separately? Happy with whatever you and David decide..
>
> Thanks,
> Usama

Removing the globals before the parallel boot series, would be the
best option IMO.  That would make the transition simpler.

--
Brian Gerst.