Re: [PATCH 0/8] x86, acpi: Move acpi_initrd_override() earlier.

[Tang Chen <tangchen@cn.fujitsu.com>]

Hi all,

This patch-set has not been fully tested. I sent them first for you
to review. Please comment if we can agree on this solution.

Thanks.:)

On 08/21/2013 06:15 PM, Tang Chen wrote:
> This patch-set aims to move acpi_initrd_override() earlier on x86.
> Some of the patches are from Yinghai's patch-set:
> https://lkml.org/lkml/2013/6/14/561
>
> The difference between this patch-set and Yinghai's original patch-set are:
> 1. This patch-set doesn't split acpi_initrd_override(), but call it as a
>     whole operation at early time.
> 2. Allocate memory from BRK to store override tables.
>     (This idea is also from Yinghai.)
>
>
> [Current state]
>
> The current Linux kernel will initialize acpi tables like the following:
>
> 1. Find all acpi override table provided by users in initrd.
>     (Linux allows users to override acpi tables in firmware, by specifying
>     their own tables in initrd.)
>
> 2. Use acpica code to initialize acpi global root table list and install all
>     tables into it. If any override tables exists, use it to override the one
>     provided by firmware.
>
> Then others can parse these tables and get useful info.
>
> Both of the two steps happen after direct mapping page tables are setup.
>
> [Issues]
>
> In the current Linux kernel, the initialization of acpi tables is too late for
> new functionalities.
>
> We have some issues about this:
>
> * For memory hotplug, we need ACPI SRAT at early time to be aware of which memory
>    ranges are hotpluggable, and prevent bootmem allocator from allocating memory
>    for the kernel. (Kernel pages cannot be hotplugged because )
>
> * As suggested by Yinghai Lu<yinghai@kernel.org>, we should allocate page tables
>    in local node. This also needs SRAT before direct mapping page tables are setup.
>
> * As mentioned by Toshi Kani<toshi.kani@hp.com>, ACPI SCPR/DBGP/DBG2 tables
>    allow the OS to initialize serial console/debug ports at early boot time. The
>    earlier it can be initialized, the better this feature will be.  These tables
>    are not currently used by Linux due to a licensing issue, but it could be
>    addressed some time soon.
>
>
> [What are we doing]
>
> We are trying to initialize acip tables as early as possible. But Linux kernel
> allows users to override acpi tables by specifying their own tables in initrd.
> So we have to do acpi_initrd_override() earlier first.
>
>
> [About this patch-set]
>
> This patch-set aims to move acpi_initrd_override() as early as possible on x86.
> As suggested by Yinghai, we are trying to do it like this:
>
> On 32bit: do it in head_32.S, before paging is enabled. In this case, we can
>            access initrd with physical address without page tables.
>
> On 64bit: do it in head_64.c, after paging is enabled but before direct mapping
>            is setup.
>
> And also, acpi_initrd_override() needs to allocate memory for override tables.
> But at such an early time, there is no memory allocator works. So the basic idea
> from Yinghai is to use BRK. We will extend BRK 256KB in this patch-set.
>
>
> Tang Chen (6):
>    x86, acpi: Move table_sigs[] to stack.
>    x86, acpi, brk: Extend BRK 256KB to store acpi override tables.
>    x86, brk: Make extend_brk() available with va/pa.
>    x86, acpi: Make acpi_initrd_override() available with va or pa.
>    x86, acpi, brk: Make early_alloc_acpi_override_tables_buf() available
>      with va/pa.
>    x86, acpi: Do acpi_initrd_override() earlier in head_32.S/head64.c.
>
> Yinghai Lu (2):
>    x86: Make get_ramdisk_{image|size}() global.
>    x86, microcode: Use get_ramdisk_{image|size}() in microcode handling.
>
>   arch/x86/include/asm/dmi.h              |    2 +-
>   arch/x86/include/asm/setup.h            |   11 +++-
>   arch/x86/kernel/head64.c                |    4 +
>   arch/x86/kernel/head_32.S               |    4 +
>   arch/x86/kernel/microcode_intel_early.c |    8 +-
>   arch/x86/kernel/setup.c                 |   93 ++++++++++++++++------
>   arch/x86/mm/init.c                      |    2 +-
>   arch/x86/xen/enlighten.c                |    2 +-
>   arch/x86/xen/mmu.c                      |    6 +-
>   arch/x86/xen/p2m.c                      |   27 ++++---
>   drivers/acpi/osl.c                      |  130 ++++++++++++++++++++-----------
>   include/linux/acpi.h                    |    5 +-
>   12 files changed, 196 insertions(+), 98 deletions(-)
>
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