linux-kernel - Re: [PATCH] ACPI: x86: Call acpi_boot_table_init() after acpi_table

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Date:   Wed, 14 Apr 2021 09:42:01 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        George Kennedy <george.kennedy@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        x86 Maintainers <x86@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH] ACPI: x86: Call acpi_boot_table_init() after
 acpi_table_upgrade()

On 13.04.21 19:53, Rafael J. Wysocki wrote:
> On Tue, Apr 13, 2021 at 7:43 PM David Hildenbrand <david@...hat.com> wrote:
>>
>> On 13.04.21 16:01, Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>
>>> Commit 1a1c130ab757 ("ACPI: tables: x86: Reserve memory occupied by
>>> ACPI tables") attempted to address an issue with reserving the memory
>>> occupied by ACPI tables, but it broke the initrd-based table override
>>> mechanism relied on by multiple users.
>>>
>>> To restore the initrd-based ACPI table override functionality, move
>>> the acpi_boot_table_init() invocation in setup_arch() on x86 after
>>> the acpi_table_upgrade() one.
>>>
>>> Fixes: 1a1c130ab757 ("ACPI: tables: x86: Reserve memory occupied by ACPI tables")
>>> Reported-by: Hans de Goede <hdegoede@...hat.com>
>>> Tested-by: Hans de Goede <hdegoede@...hat.com>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>> ---
>>>
>>> George, can you please check if this reintroduces the issue addressed by
>>> the above commit for you?
>>>
>>> ---
>>>    arch/x86/kernel/setup.c |    5 ++---
>>>    1 file changed, 2 insertions(+), 3 deletions(-)
>>>
>>> Index: linux-pm/arch/x86/kernel/setup.c
>>> ===================================================================
>>> --- linux-pm.orig/arch/x86/kernel/setup.c
>>> +++ linux-pm/arch/x86/kernel/setup.c
>>> @@ -1045,9 +1045,6 @@ void __init setup_arch(char **cmdline_p)
>>>
>>>        cleanup_highmap();
>>>
>>> -     /* Look for ACPI tables and reserve memory occupied by them. */
>>> -     acpi_boot_table_init();
>>> -
>>>        memblock_set_current_limit(ISA_END_ADDRESS);
>>>        e820__memblock_setup();
>>>
>>> @@ -1132,6 +1129,8 @@ void __init setup_arch(char **cmdline_p)
>>>        reserve_initrd();
>>>
>>>        acpi_table_upgrade();
>>> +     /* Look for ACPI tables and reserve memory occupied by them. */
>>> +     acpi_boot_table_init();
>>>
>>>        vsmp_init();
>>
>> This is fairly late; especially, it's after actual allocations -- see
>> e820__memblock_alloc_reserved_mpc_new().
>>
>> Can't the table upgrade mechanism fix up when adjusting something?
> 
> Not at this point of the cycle I'm afraid.
> 
>> Some details on what actually breaks would be helpful.
> 
> Generally speaking, the table overrides that come from the initrd are
> not taken into account if acpi_boot_table_init() runs before
> acpi_table_upgrade() and the latter cannot run before
> reserve_initrd().

I see. (looking at Documentation/acpi/initrd_table_override.txt I 
understand what acpi table overrides are for :) )

> 
> Honestly, I'm not sure how much effort it would take to untangle this ATM.

Also true; ideally, we wouldn't have any allocations (find+reserve) 
before ordinary reservations are done.

However, I have no idea if we can move 
e820__memblock_alloc_reserved_mpc_new() and reserve_real_mode() around 
easily. Also, reserve_initrd()->relocate_initrd() does allocations.

This is a mess.

-- 
Thanks,

David / dhildenb