linux-kernel - Re: [PATCH v5 0/3] x86: make rsdp address accessible via boot params

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Date:   Wed, 10 Oct 2018 08:23:52 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org, linux-doc@...r.kernel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com, corbet@....net,
        boris.ostrovsky@...cle.com,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v5 0/3] x86: make rsdp address accessible via boot params


* Juergen Gross <jgross@...e.com> wrote:

> In the non-EFI boot path the ACPI RSDP table is currently found via
> either EBDA or by searching through low memory for the RSDP magic.
> This requires the RSDP to be located in the first 1MB of physical
> memory. Xen PVH guests, however, get the RSDP address via the start of
> day information block.
> 
> In order to support an arbitrary RSDP address this patch series adds
> the physical address of the RSDP to the boot params structure filled
> by the boot loader.
> 
> Juergen Gross (3):
>   x86/xen: fix boot loader version reported for pvh guests
>   x86/boot: add acpi rsdp address to setup_header
>   x86/acpi: take rsdp address for boot params if available
> 
>  Documentation/x86/boot.txt            | 32 +++++++++++++++++++++++++++++++-
>  arch/x86/boot/header.S                |  6 +++++-
>  arch/x86/include/asm/acpi.h           |  7 +++++++
>  arch/x86/include/asm/x86_init.h       |  2 ++
>  arch/x86/include/uapi/asm/bootparam.h |  4 ++++
>  arch/x86/kernel/acpi/boot.c           |  6 ++++++
>  arch/x86/kernel/head32.c              |  1 +
>  arch/x86/kernel/head64.c              |  2 ++
>  arch/x86/kernel/setup.c               | 17 +++++++++++++++++
>  arch/x86/kernel/x86_init.c            |  3 +--
>  arch/x86/xen/enlighten_pvh.c          |  2 +-
>  11 files changed, 77 insertions(+), 5 deletions(-)

I have some vague memories of an older variant of this feature breaking stuff and resulting in 
me involuntarily participating in an overly long bisection session.

If that memory is right and I'm not confusing it with some other patchset, could you please 
provide some more context, what that old problem was, how it was resolved, whether it is 
expected to trigger on any machines, etc., to create some warm fuzzy feelings about this 
patch-set and to reduce my bisectofobia? ;-)

Thanks,

	Ingo