Re: [PATCH] ACPI: x86: Call acpi_boot_table_init() after acpi_table_upgrade()

["Rafael J. Wysocki" <rafael@kernel.org>]

On Tue, Apr 13, 2021 at 7:43 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 13.04.21 16:01, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.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@redhat.com>
> > Tested-by: Hans de Goede <hdegoede@redhat.com>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.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().

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